Understanding Neonatal : Building Knowledge to Advance Practice

Nicole T. de Silva, RN, MSc Jennifer A. Young, RN, MN Paul W. Wales, MD, MSc, FRCS(C)

eonata l intestinal obstruction arises from the tract is to transport enteral nutrients, fluids, and gases so Nvarious congenital anomalies of the gastrointestinal that digestion may occur. Knowledge of some key anatomic (GI) tract, as well as from acquired conditions. Common landmarks and structures is essential to understanding the clinical features include a history signs and symptoms that present of , vomit- when the GI tract becomes ing, abdominal distension, and Abstract obstructed (Figure 1). The GI failure to pass in Providing care to neonates with bowel obstruction tract can be divided into three the first 24–48 hours of life. A requires a basic understanding of gastrointestinal (GI) major anatomic and functional detailed history, careful physi- anatomy and functional landmarks as well as knowledge of areas: (1) the proximal GI tract, the pathophysiology associated with intestinal blockage. cal examination, and subse- including the oral cavity, the Early recognition and prompt diagnosis necessitate astute quent radiographic imaging and assessment of common presenting symptoms and accurate , and the ; investigations help the neonatal interpretation of diagnostic investigations. Initial medical (2) the , made up nurse and nurse practitioner to management is focused primarily on gastric decompression of the , the support the infant appropriately and maintenance of fluid and electrolyte balance. This that begins just distal to the lig- in the face of a potential life- article describes features of the neonatal GI tract and ament of Treitz, and the ; ­threatening event. This article is discusses common causes of neonatal bowel obstruction. and (3) the large bowel, includ- intended to advance the knowl- ing the cecum with appendix, edge of neonatal nurses regard- the colon, and the . The ing the diagnostic evaluation and initial management of smooth muscle (circular and longitudinal) layers of the GI infants with suspected intestinal obstruction. To understand tract are innervated by nerve cells called ganglia. In normal the etiology of symptoms, clinical presentation, and diag- circumstances, impulses from the ganglion cells result in nostic methods, health care providers must know the basic rhythmic constriction and relaxation of the bowel wall (peri- anatomy of the GI tract. Also reviewed here are the common stalsis), thus propelling the GI tract contents distally.1 causes of congenital intestinal obstruction that occur between Transition zones consisting of muscular tissue, referred the gastric outlet and the . to as valves or sphincters, act as “gatekeepers” or “brakes” to control the transit time of nutrients from one functional area Anatomic and Functional to another. The flow of nutrients is slowed to allow enough Landmarks of the GI Tract time for the digestive process to occur. The most proxi- The GI tract is a conduit that extends from the proximal mal brake is the , which is positioned between the oral cavity to the distal rectum and anus. The purpose of stomach and the duodenum. The more distal brakes include

Accepted for publication May 2005. 25 Years N EONATAL N ETWORK VOL. 25, NO. 5, s e p t e m b e r / o c t o b e r 2 0 0 6 3 0 3 Figure 1 n Selected gastrointestinal anatomy.

Courtesy of The Hospital for Sick Children, Toronto, Ontario. the ileocecal valve, which lies between the small and large the common duct. Bile is stored in the gall bladder when intestine, and the anal sphincter and anus, which hold waste produced in excess. The gall bladder secretes bile into the in the rectum in preparation for evacuation from the body. common , which empties into the second or descend- Knowing where these functional brakes are located is impor- ing part of the duodenum at the major papilla (ampulla of tant, particularly for the purpose of diagnostic imaging. Vater) a few centimeters distal to the pylorus.3 The bile tints Three main that arise from the abdominal aorta GI fluid green, and the presence or absence of bile-stained supply the major regions of the GI tract. The (, fluid is useful for evaluating the location of an obstruction. esophagus, stomach, and proximal duodenum before the opening of the bile duct) obtains its blood supply from the Types of Obstruction celiac . The midgut (small intestine, cecum, appendix, A blockage anywhere along the GI tract may be struc- and ascending and proximal transverse colon) is supplied by tural (mechanical) or physiologic (functional) (Table 1). the superior mesenteric artery. The hindgut (distal transverse Mechanical obstructions are more likely to require opera- colon, descending colon, sigmoid, and upper rectum) is sup- tive repair than functional (or paralytic) obstructions, which plied by the inferior mesenteric artery.2 Vascular insufficiency usually require medical treatment. A mechanical obstruction from thrombosis, strangulation, or low flow states can disrupt is usually caused by an intramural structural anomaly, such as the arterial supply of the bowel and lead to ischemic or an atresia, a , or a web. (Table 2 provides definitions malformation during any phase of development. and illustrations.) Mechanical obstructions physically slow or Three accessory digestive organs secrete substances block the forward flow of gas, fluids, and nutrients within the directly into the proximal GI tract: the , liver, and lumen, either partially or completely. Mechanical obstruc- gall bladder (see Figure 1). The pancreas secretes digestive tions, whether intraluminal or extraluminal and whether enzymes that drain into the pancreatic duct and empty pre- partial or complete, result in a narrowing of the diameter of dominantly into the duodenum at the ampulla of Vater. The the intestinal lumen. liver produces bile, which is emptied into the duodenum via

25 Years N EONATAL N ETWORK 3 0 4 s e p t e m b e r / o c t o b e r 2 0 0 6 , VOL. 25, NO. 5 n Table 1 Secondary Method of Classifying Intestinal Obstruction* Fluid and Electrolyte Imbalance Mechanical In comparison to adults, neonates secrete large volumes Intraluminal (within bowel lumen) of gastrointestinal fluids and electrolytes for their weight. If Meconium (complicated and uncomplicated) all of the gastric content is lost through vomiting, short-lived Intraluminal tumor masses compensation occurs through depletion of the extracellular Extraluminal (outside of bowel lumen) fluid volume.4 In general, the obstructed bowel continues to Bands (adhesive, congenital Ladd’s-malrotation) secrete fluid, but reabsorption of the fluid and electrolytes is Masses (tumors, lymphoid tissue, cysts—duplication, ovarian, mesenteric) compromised. The amount and type of fluid loss depends on Hernias (inguinal, diaphragmatic, internal) the location of the obstruction. The degree of obstruction Intramural (within bowel wall) (partial or complete) and the extent of the vascular response Atresia/web/stenosis of the bowel wall (e.g., decreased stroke volume, hypotension) are directly Strictures (postinjury—i.e., necrotizing enterocolitis, ischemic injury) related to the amount of the fluid deficit.5 Strangulating Intussusception obstructions produce large fluid and serum protein loss as a Volvulus result of transudation (ascites) from the intestinal lymphatics Hirschsprung’s disease and increased mucosal permeability.5,6 Functional (Loss of Peristalsis) Bacterial Translocation Pseudo-obstruction (neuropathic or myopathic in origin) After delivery, the baby’s gut becomes rapidly colonized Ileus with bacteria, especially if feeding has occurred.7 Intestinal Sepsis obstruction can lead to sepsis secondary to the overgrowth of Electrolyte imbalance (hypocalcemia, hypokalemia) these enteric organisms.8,9 The multiplication of bacteria and Narcotic induced the production of endotoxins quickly result in saturation of Metabolic (hypothyroidism) the mesenteric nodes, the lymphatic system, and the venules Retroperitoneal hematoma and eventual bacterial penetration of the bowel wall (bacte- Meconium plug syndrome rial translocation) into the bloodstream.10–12 Postoperative (handling/trauma) Prematurity/immaturity Circulatory Disturbances * As conceptualized by the authors The nutrient vessels encircle the bowel with a fine network of capillaries emanating from the . In the pres- ence of distention that increases the intraluminal pressure, Functional (physiologic) obstructions are caused by blood shunts away from the capillary bed.13 Mucosal oxygen decreased intestinal motility due to a direct inhibition of consumption decreases, and capillary venous congestion the smooth muscle in the bowel wall. Consequently, distal occurs. As engorgement progresses, the arterial blood supply propulsion of the contents of the bowel fails or is slowed. A decreases, and /infarction occurs.14,15 The brunt of combination of mechanical and functional obstructions may the circulatory compromise is borne by the dilated bowel just occur. Overall, obstructions can be further subdivided by proximal to the point of obstruction.16,17 location within the GI tract: proximal (just before or after Intraluminal distention alone is not the primary cause the ampulla of Vater), mid (jejunoileal), or distal (colonic). of bowel ischemia and ulceration. Perforation most likely is The bowel wall is compliant and can change shape to a result of a cascade of events, including increased intralu- accommodate varying amounts of gas, fluid, or solids. The minal pressure, bacterial translocation, and the response of urgency of the obstruction is secondary to the risk of extreme the intestinal microvasculature to bacterial endotoxins that dilation proximal to the obstruction, compromise of intes- results in necrosis or gangrene.18 tinal integrity by strangulation or constriction of the blood vessels and tissues, and ischemic injury that may result in Congenital Intestinal Obstructions necrosis and eventual perforation. The six major congenital causes of neonatal intestinal obstruction are found in the proximal, mid, and distal GI Pathophysiology of tract. Atresia is the most common cause of congenital intes- Intestinal Obstruction tinal obstruction and accounts for approximately one-third Intestinal obstruction can lead to three major problems: of cases of obstruction in neonates.19 Following are descrip- fluid and electrolyte imbalance, translocation of bacteria from tions of the presenting symptoms and radiographic findings the gut to the bloodstream, and circulatory compromise of of these causes, as well as a review of the diagnostic tools the bowel wall. Because these problems can lead to shock, used and initial medical management required. respiratory and renal failure, and local or generalized sepsis, urgent evaluation and intervention are essential.

25 Years N EONATAL N ETWORK VOL. 25, NO. 5, s e p t e m b e r / o c t o b e r 2 0 0 6 3 0 5 TABLE 2 n Illustrated Glossary of Common Terminology

One end of bowel closed or ending in a blind pouch Atresia May be single or multiple, causing sausagelike appearance of bowel

Stenosis Narrowing of segment of bowel

Film or web of tissue partially or completely Web blocking internal lumen of bowel

Windsock Billowing of web of tissue

Development of scar tissue between bowel Adhesive band loops; may compress lumen externally May occur after or

Volvulus Twisting of bowel

Large meconium plug and meconium Meconium ileus pellets in terminal ileum as typically seen in meconium ileus

Pancreas growing in the form of an encircling ring around the duodenum, causing extrinsic compression

Courtesy of The Hospital for Sick Children, Toronto, Ontario.

Mechanical Obstructions: Proximal GI Tract development.21 On examination, the mid and Duodenal Obstructions (Atresia, Stenosis, lower abdomen may be scaphoid. Abdominal or Web). Congenital abnormalities of the duo- x-rays frequently demonstrate the presence of a denum lead to a partial or complete blockage of “double bubble” (Figure 2). The first bubble, the intestinal lumen. This blockage most com- usually the larger of the two, represents air in the monly occurs just distal to the ampulla of Vater distended stomach, and the second represents (entrance of the bile duct into the duodenum), air in the first portion of the duodenum. The resulting in bilious vomiting.20 pylorus separates the two bubbles. If the second is likely caused by a failure of recanilization of bubble is elongated, there may be a windsock the lumen of the duodenum during embryologic deformity that can be described as a billowing of

25 Years N EONATAL N ETWORK 3 0 6 s e p t e m b e r / o c t o b e r 2 0 0 6 , VOL. 25, NO. 5 Figure 2 n Abdominal x-ray demonstrating “double bubble.” Figure 3 n Normal attachment of small bowel mesentery. Mesenteric attachment extends from ligament of Treitz (left upper quad- rant) to cecum (right lower quadrant).

a web of tissue distally (see Table 2). In the case of complete ­obstruction (atresia or web), no air appears in the distal bowel on abdominal x-ray. If air is seen distal to the double bubble, the duodenum is likely stenosed rather than atretic. Immediate upper GI contrast studies are required to make the diagno- sis and rule out life-threatening malrotation with volvulus. Approximately one-third of neonates experiencing duodenal atresia will also have . These infants may also From: Filston HC, and Kirks DR. 1981. Malrotation—the ubiquitous experience cardiac, renal, and other GI anomalies, and evalua- anomaly. Journal of 16(4): 616. Reprinted by tion for these anomalies is warranted.22 permission. Annular pancreas presents similarly to duodenal obstruc- tions. Annular pancreas is recognized as an embryonic abnormality demonstrated by an incomplete rotation around between the ligament of Treitz in the left upper quadrant and the duodenum, which causes external compression of the the cecum in the right lower quadrant (Figure 3).23,24 duodenum. Malrotation is a congenital abnormality in which this Malrotation (with or without Volvulus). The gut is complex embryologic sequence of intestinal rotation and fix- originally a midline structure. Three stages of intestinal rota- ation does not occur and represents a neonatal surgical emer- tion occur between weeks 4 and 12 of embryogenesis. Stage gency. The duodenojejunal loop fails to rotate around the 1 is represented by the physiologic herniation of the gut as it SMA and remains on the right side of the abdomen while the grows faster than the fetus and therefore exits the abdomen cecocolic loop remains abnormally situated on the left side of through the umbilical ring. In Stage 2, the bowel returns to the abdomen. The two points of fixation are therefore close the abdominal cavity and rotates 270 degrees counterclock- together, resulting in a narrow mesenteric pedicle (Figure 4). wise around the superior mesenteric artery (SMA). Stage 3 A narrow, poorly fixed mesentery is at risk of twisting (vol- is identified by peritoneal fixation of the duodenum and by vulus) and occluding the intestinal lumen, resulting in inter- the ascending and descending colon. The base of the mes- ruption of intestinal blood supply and leading to potential entery is normally wide and is fixed along the posterior wall infarction of the whole midgut.24

25 Years N EONATAL N ETWORK VOL. 25, NO. 5, s e p t e m b e r / o c t o b e r 2 0 0 6 3 0 7 Figure 4 n Malrotation. Figure 5 n Upper GI contrast study showing A. Nonrotation. B. Incomplete rotation. C. Potential for development of midgut volvulus. whirlpool effect consistent with malrotation.

From: Filston HC, and Kirks DR. 1981. Malrotation—the ubiquitous anomaly. Journal of Pediatric Surgery 16(4): 616. Reprinted by permission. has been proposed that an intrauterine vascular accident—such as an embolus, thrombus, or antenatal volvulus—causes jejunal and ileal obstructions.26 Typical symptoms in malrotation are bilious vomiting and a scaphoid Jejunoileal obstructions have been cat- abdomen. With volvulus, the abdomen may be distended and tender, and egorized into five types (Figure 6): Type I, a the patient may be lethargic, pass bloody stool, and demonstrate general simple intraluminal membrane; Type II, a cord signs of shock. An abdominal x-ray illustrates a scanty or gasless pattern anomaly at the locus of the atresia; Type IIIA beyond the duodenum. An upper GI series demonstrates a dilated stomach (most common), the separation of both ends of and duodenum with minimal contrast distal to the duodenum; the image the bowel by a mesenteric defect; Type IIIB, an may resemble a whirlpool (Figure 5). The upper GI series identifies the “apple peel” deformity, with the bowel short- ligament of Treitz in the right abdomen with malrotation (normally to the ened and the circulation provided retrograde left of the spinal column at the level of the pylorus). An ultrasound may by the ileocolic artery around which the bowel also identify an abnormal SMA and superior mesenteric vein orientation, revolves; and Type IV, two or more intestinal but is not a sensitive investigation for determining a malrotation defect. segments, resembling “sausage links,” as a result Malrotation with volvulus is considered a surgical emergency second- of multiple mesenteric defects.26 ary to the risk of strangulation of the blood supply. Immediate surgical Atresia is more common in the jejunum correction is necessary to untwist the bowel, re-establish the intestinal than in the ileum and is extremely rare in the vascular blood supply, and prevent intestinal ischemic injury and infarc- colon.27,28 Infants with jejunal atresia present tion. Any neonate who presents with bilious emesis must therefore have an with bilious vomiting and mild abdominal dis- upper GI contrast study to rule out malrotation. The upper GI study must tension. The abdominal x-rays reveal dilated be performed immediately because, in the presence of volvulus, a delay in loops, air-fluid levels, and, in some cases, a repair can result in midgut necrosis and patient death. “triple bubble” (Figure 7).29 Intestinal air does Malrotation also causes obstruction without volvulus. Peritoneal bands not appear distal to the obstruction. (Ladd’s bands) that extend from the right abdominal wall to the cecum Ileal atresia presents with bilious vomiting arise from an abnormal rotation of the duodenum and small bowel.25 as well, but usually also with more significant The bands cross the duodenum and cause obstruction by extrinsic abdominal distention. The contrast enema is compression. the diagnostic test of choice because any con- trast given from the upper GI usually dilutes Mechanical Obstructions: Mid GI Tract and cannot pinpoint an obstruction by the Jejunoileal Obstructions. Atresia is the cause of nearly 95 percent of time it reaches the distal bowel. The contrast jejuno-ileal obstructions, and stenosis causes the remaining 5 percent.20 It enema reveals a small, empty, unused colon, or

25 Years N EONATAL N ETWORK 3 0 8 september/october 2 0 0 6 , V O L. 2 5 , N O . 5 Figure 6 n Classification of jejunoileal atresia. Figure 7 n Abdominal x-ray demonstrating “triple A. Type I: Mucosal (membranous) atresia with intact bowel wall and mesentery. B. Type bubble” as seen in jejunoileal atresia. II: Blind ends are seperated by a fibrous cord. C. Type IIIA: Blind ends are separated by a V-shaped mesenteric defect (gap). D. Type IIIB: Apple peel atresia. E. Type IV: Multiple atresias (string of sausages).

Figure 8 n Contrast enema demonstrating microcolon.

From Grosfeld JL, Ballantine TV, and Shoemaker R. 1979. Operative management of and stenosis based on pathologic findings. Journal of Pediatric Surgery 14(3): 369. Reprinted by permission.

­microcolon, with intestinal atresia (Figure 8). Once the contrast is refluxed proximal to the ileocecal valve, the level of the obstruction can be deter- mined. If the terminal ileum is small and ends abruptly, then small bowel atresia is suspected. Meconium ileus is diagnosed if the contrast enema reveals meconium pellets in the terminal ileum.29 Meconium Ileus (Complicated and Uncomplicated). Meconium ileus is an obstruction caused by inspissated, tenacious meconium that adheres to the mucosa of the distal small bowel (terminal ileum). A pancreatic enzyme deficiency or an abnormality in the composition of the meconium causes it to be denser and more “sticky” than usual. Twenty to 30 percent of infants with present with meconium ileus.30–32 Meconium ileus can be categorized as complicated or uncomplicated. In cases of complicated meconium ileus, intestinal atresias, volvulus, and/ or perforation occur. Complications arise as the meconium obstructs segment of intestine may be completely resorbed, the terminal ileum and progressive distention leads to volvulus and isch- resulting in an atretic end.33 Antenatal perfora- emic injury. If the volvulus occurs early enough in gestation, the affected tion of the bowel may result in formation of a

25 Years N EONATAL N ETWORK VOL. 25, NO. 5, s e p t e m b e r / o c t o b e r 2 0 0 6 3 0 9 Figure 9 n Lateral view of contrast enema demonstrating also identifies the microcolon and outlines meconium pellets transition zone seen in Hirschsprung’s disease. in the terminal ileum.40 Complicated forms of meconium ileus often require car- diovascular and respiratory support along with urgent explor- atory . In cases of uncomplicated meconium ileus, the contrast enema may be therapeutic; the water-soluble contrast medium can assist with separating the meconium from the bowel wall.41–43 Bowel irrigation or enemas with proteolytic agents such as N-acetylcysteine (Mucomyst) can also be effective.20,38 Rarely is surgical intervention required in cases of uncomplicated meconium ileus. All patients should be screened for cystic fibrosis.

Mechanical Obstructions: Distal GI Tract Hirschsprung’s Disease. Hirschsprung’s disease (HD) is a congenital absence of enteric ganglia most commonly seen in a segment of the large bowel. Ganglion cells originate early in embryogenesis from the neural crest and migrate into the embryonic intestine in a descending direction. Enteric ganglia are necessary for normal peristalsis and motility. When ganglion cells are absent, the proximal segment of bowel becomes dilated and hypertrophied as a result of the dysmotile distal bowel. HD may involve the entire colon and portions of the small bowel. The rectosigmoid region of the large bowel is most typically affected, and the total colon is involved in 5 to 10 percent of infants with HD. Fewer than 1 percent of infants with HD have aganglionosis of the entire length of the intestinal tract.44 Common presenting symptoms of HD are abdominal dis- meconium pseudocyst, with the meconium that has spilled tension and failure to pass meconium and may also include into the peritoneal cavity appearing as a “pseudo” (or false) feeding intolerance and bilious emesis. An abdominal x-ray cyst.34 Fetal ultrasounds usually reveal echogenic bowel or illustrates dilated loops of bowel with or without air in the evidence of intra-abdominal calcifications.35 Problems arise rectum. A contrast enema demonstrates a transition zone postnatally with perforation and meconium pseudocyst between the smaller, aganglionic distal bowel (rectum) and because they result in extensive adhesions and a chemical the dilated proximal bowel (Figure 9).45 The transition zone peritonitis secondary to an inflammatory response.33 may demonstrate a sudden funnel with sharp, angular bowel Uncomplicated (or simple) meconium ileus occurs when walls. The contrast study may reveal very “ragged” bowel pellets of meconium obstruct the distal small bowel.36 It walls that may represent Hirschsprung’s enterocolitis. Rectal occurs more often in premature or very biopsy is required for definitive diagnosis by confirming the infants than in term infants.37,38 In both complicated and absence of ganglion cells. uncomplicated meconium ileus, the unused portion of the The etiology of HD is unknown, but the disease can bowel distal to the obstruction is often small and is consid- be associated with genetic problems including Down syn- ered a microcolon.35 drome or congenital central hypoventilation syndrome.46,47 Common clinical features include abdominal distention Approximately 10 percent of children with HD have a posi- within 24 to 48 hours after birth and failure to pass stool. tive family history for Hirschsprung’s disease.44 Manifestations of are evident if ante- Imperforate Anus. Imperforate anus causes distal intes- natal bowel perforation has occurred. These signs include tinal obstruction and occurs when the rectum fails to com- gross distention, abdominal wall discoloration, and tender- pletely descend, resulting in the absence of an anal opening.23 ness associated with hematologic, metabolic, and respiratory This anomaly can be classified as high or low, depending on complications.39 Abdominal x-rays reveal dilated loops and the level of the rectal pouch (Figure 10). A high defect occurs occasionally a “bubbly” appearance of the stool mixed with when the rectum terminates above the pelvic floor muscula- fluid in the bowel proximal to the inspissated meconium.29 ture; lower defects occur when the incomplete descent ends Ultrasounds of the abdomen may reveal ascites. A contrast below the pelvic floor musculature. Failure to pass stool, enema is diagnostic, particularly if the contrast can reflux abdominal distension, and bilious emesis are common present- proximally through the ileocecal valve. The contrast enema ing symptoms. Radiographic imaging, including abdominal

25 Years N EONATAL N ETWORK 3 1 0 s e p t e m b e r / o c t o b e r 2 0 0 6 , VOL. 25, NO. 5 Figure 10 n Classification of high and low imperforate anus in male and female.

Courtesy of The Hospital for Sick Children, Toronto, Ontario. x-ray, is necessary preoperatively to determine the level of the plug syndrome does not appear to be associated with cystic rectal pouch relative to the pubococcygeal line. Pelvic ultra- fibrosis or HD, but is more common in premature infants.50 sound may be indicated to identify a low-lying pouch and This finding may be related to immature ganglion cell devel- facilitate decision making regarding treatment. Infants with opment in preterm infants.37 lower anomalies can be expected to have normal rectal integ- Treatment involves a regimen of colonic washouts with rity after repair, whereas infants with higher defects may have repeated enemas or with rectal stimulation (digital or with difficulty with rectal continence.48 suppositories). Some evidence indicates that treatment with Other congenital anomalies can be associated with imper- mucolytic enemas such as N-acetylcysteine (Mucomyst) can forate anus, particularly genitourinary and esopha- also be effective for the premature population.38 HD, cystic geal atresia with or without tracheoesophageal fistulas.23 For fibrosis, and endocrine disorders (adrenal and thyroid) need this reason, infants presenting with imperforate anus require to be investigated if repeated enemas or rectal stimulation do additional investigation to rule out anomalies consistent with not resolve the meconium plug. VACTERL association. VACTERL association is an acronym Paralytic Ileus. A paralytic ileus is a functional obstruc- representing broad categories of potential anomalies that may tion of the intestines secondary to a transient loss of peristaltic arise in infants with imperforate anus: V-vertebral, A-anal, activity. Both local and systemic factors cause it. Local factors C-cardiac, TE-tracheo-esophageal , , include surgical manipulation of the bowel, peritonitis, isch- R-renal, L-limbs. emic injury, retroperitoneal bleeding, and spinal surgery.18 Systemic factors include sepsis, electrolyte imbalance (hypo- Functional Obstructions calcemia, hypokalemia), uremia, and diabetic ketoacidosis. Meconium Plug Syndrome. Meconium plug syndrome Paralytic ileus in the neonate can be a confounding factor represents a transient large bowel obstruction relieved by in the development of a differential diagnosis for congeni- the passage of meconium plugs (by suppository, enema, or tal obstruction, especially if the infant is septic. Presentation rectal washout). This obstruction presents with abdominal mimics presentation for mechanical obstruction except for distention, failure to pass stool, and bilious vomiting. With the notable absence of bowel sounds. Diagnosis by abdomi- diagnostic contrast enemas, or upon rectal exam, a “whitish” nal film usually reveals dilated loops, air throughout the small plug containing epithelial cells is passed, followed by meco- and large bowel (without any specific locus of obstruction), nium, often with resolution of the symptoms.49 Meconium and a lack of assymetric loops.51,52 Treatment includes gastric

25 Years N EONATAL N ETWORK VOL. 25, NO. 5, s e p t e m b e r / o c t o b e r 2 0 0 6 3 1 1 Figure 11 n Abdominal x-ray with GI tract anatomic landmarks. A plain abdominal radiograph in most cases reveals the characteristic distended gas-filled bowel loops proximal to the obstruction (Figure 12). Air fluid levels may also be evident because the fluid ingested or produced within the GI tract is unable to pass beyond the obstruction.29,54 The number of dilated loops often corresponds to the level of obstruction—that is, the more dilated loops, the more distal the obstruction.53 Typically, abdominal films are taken with anterior- ­posterior and lateral beams, as well as in the lateral decubitus position. Rarely are upright or inverted films completed in the neonate.

Contrast Studies The placement of radio-opaque fluid (e.g., Omnipaque) into the GI tract highlights any abnormalities of anatomy (i.e., the location of the stomach and the size, caliber, and location of the small and large bowel) and can be used to locate the position and type of obstruction, either complete or partial. The contrast may reveal a blind atretic end of bowel or slowly pass through a narrowed stenosed area. The contrast may flow around meconium to reveal filling defects (areas that contain meconium do not usually appear as opaque), or it may outline abnormalities such as cysts or tumors.55 Two types of contrast studies generally rule out obstruc- tion. The choice (upper vs lower) and the sequence of studies are determined by the clinical presentation, the x-ray find- ings, and the suspicion of upper vs lower GI tract obstruc- tion.53,55 For instance, if a proximal obstruction such as From: Quinn D, and Shannon LF. 1995. Congenital anomalies of the gas- duodenal atresia or malrotation is suspected, the condition is trointestinal tract. Part I: The stomach. Neonatal Network 14(8): 64. first investigated by the upper GI series (e.g., ESSB) because the contrast immediately outlines the esophagus (E), stomach (S), and proximal small bowel (SB). Over time, the contrast flows into the small bowel, and eventually the colon becomes decompression, fluid and electrolyte support, and diagnosis opaque. The contrast becomes diluted and thus less radio- and treatment of the underlying problem. Once the causative opaque, however, decreasing the usefulness of this investiga- condition has been resolved, the tone of the bowel can be tion for diagnosing distal obstructions.53 expected to return to normal.18 If a mid to distal obstruction is suspected, the contrast enema is done first to assess the patency of the distal bowel. Diagnostic Tools Within minutes, the contrast outlines the distal bowel, includ- Radiographs and other diagnostic aids, such as contrast ing the rectum, sigmoid, remainder of the colon, cecum, and studies, ultrasounds, and computed tomography (CT) scans, appendix. The goal is to ensure that the contrast medium also have specific diagnostic roles in the investigation of intestinal refluxes through the ileocecal valve into the terminal ileum obstruction in the neonate. to rule out distal small bowel obstructions.55 Problems occur if the contrast from the ESSB mixes with contrast from the Radiograph (X-Ray) enema. In those circumstances, the contrast enema must be Air is generally present in the stomach of the neonate repeated once the contrast material from the proximal study within 5 minutes of life, in the jejunum within 15 minutes, has been evacuated, potentially causing delays. In some cases, and in the cecum by 2 to 3 hours. Air usually reaches the the contrast enema can be diagnostic and therapeutic, essen- sigmoid colon and the rectum within 6 to 12 hours.52 tially removing or washing out the obstruction (meconium) Although radiographs permit visualization of the bowel gas from the distal bowel. pattern, it is difficult to differentiate between the small bowel Traditionally, barium has been used as a contrast medium. and the colon in a neonate.53 Figure 11 shows the outline of It is inexpensive, readily available, and provides good con- anatomic structures of the GI tract typically seen in a neo­ trast images. However, disadvantages for its use in the natal X-ray.25 neonate include aspiration into the lung or solidification in

25 Years N EONATAL N ETWORK 3 1 2 s e p t e m b e r / o c t o b e r 2 0 0 6 , VOL. 25, NO. 5 Figure 12 n Pictoral depiction of gas patterns seen on abdominal x-rays in cases of bowel obstruction. Proximal GI Tract Mid GI Tract Distal GI Tract

Duodenal Atresia/Web Jejunal Atresia/Web Hirschsprung’s Disease Annular Pancreas Ileal Atresia/Web Anorectal Malformations Malrotation Meconium Ileus Meconium Plug Syndrome Courtesy of The Hospital for Sick Children, Toronto, Ontario.

the bowel proximal to an obstruction (e.g., dysmotility syn- such as duplication cysts, tumors, or other masses.58 The dromes, stasis, meconium ileus). In cases of perforation, the abdominal CT scan gives detailed pictures of the viscera solid clumps of barium may form granulomas that must be (hollow and solid) as well as of fluid collections, abscesses, surgically removed. Preferably, water–soluble, nonionic, or and tumors, and it may depict other causes of an acute low-osmolar contrast solutions that readily evacuate from obstruction.59 the bowel and, in cases of perforation, are reabsorbed are used.41,53 These newer media have replaced the older high- Biopsy osmolar ones that may have led to marked fluid and eletrolyte Biopsy of the bowel tissue is usually done to observe for shifts in the neonate.53 ganglion cells in the distal GI tract (to rule out Hirschsprung’s disease, for example).20 A suction biopsy can be performed Ultrasound at the bedside; although it may appear uncomfortable, the Ultrasound of the abdomen helps to determine the ana- procedure is painless because there are no pain fibers in the tomic position of the organs as well as the position and blood rectal mucosa. Analysis by an experienced pathologist is flow of the vessels supplying and draining the abdominal essential for accurate interpretation. If the suction biopsy is organs (e.g., SMA and vein).56 It may also identify intralumi- diagnostically inconclusive, a full-thickness bowel biopsy is nal contents (e.g., meconium) as well as extraluminal masses necessary under anesthesia.20,60 Biopsy of the upper GI tract (cysts, tumors) that may obstruct the GI tract.53 Ultrasound is rarely required unless functional pathology (motility dis- of the bowel allows for assessment of (1) peristalsis (observa- order) is suspected. tion of paralytic ileus), (2) intussusception, (3) blood flow to the bowel wall, (4) air within the bowel wall (pneumatosis Clinical Presentation intestinalis) in cases of necrotizing enterocolitis, and (5) free Three classical features present in a neonate with an air and fluid outside the bowel lumen.57 intestinal obstruction: vomiting, abdominal distention, and failure to pass meconium stool.51 Secondary symp- CT Scan toms such as brady- or tachycardia, temperature instability, CT is never the initial investigation to rule out bowel twitching, and lethargy are usually a result of dehydration, obstruction, but it may be useful for detecting rarer disorders electrolyte imbalance, and sepsis.39 The characteristics

25 Years N EONATAL N ETWORK VOL. 25, NO. 5, s e p t e m b e r / o c t o b e r 2 0 0 6 3 1 3 Table 3 n Common Mechanical Congenital Intestinal Obstructions: Presentation and Diagnostic Findings Antenatal Associated Abdominal Emesis X-Ray Diagnostic Initial Diagnosis Meconium Findings Anomalies Symptoms ± Bile Findings Tests Therapy Duodenal Polyhydraminos 21 Scaphoid Yes Normal Double bubble Upper GI Surgical obstructions Dilated ± cardiac abdomen No if (usually no No or slow therapy duodenum preampulla distal gas) contrast to (<5%) distal bowel Malrotation Possible bile- + Volvulus Scaphoid Yes Initial Double or Urgent upper GI Emergent Upper stained or upper passage, triple bubble No or slow surgical amniotic fluid abdominal then none (scattered to contrast to therapy distention no distal gas) distal bowel Whirlpool effect

Jejunoileal atresia Bile-stained No  Distention Yes Initial Triple bubble Contrast enema Surgical amniotic fluid with more passage, Few dilated Microcolon therapy Possible dilated distal then none loops evident loops obstruction Meconium ileus Echogenic Cystic Distended Yes Failure to pass Scattered Contrast enema Surgical (complicated) bowel fibrosis abdomen meconium dilated loops Microcolon therapy Meconium ± volvulus ± engorged ± calcifications Inspissated stool calcifications ± atresia abdominal Soap sud/foamy vasculature Mid ± pseudocyst appearance of stool Meconium ileus None Cystic Distended Yes Failure to pass Multiple dilated Contrast enema Enema(s) (uncomplicated) fibrosis abdomen meconium loops Microcolon Bowel Meconium irrigation pellets in ± Mucomyst terminal ileum Surgical therapy rare Hirschsprung’s None Trisomy 21 Distended Yes Failure to pass Multiple dilated Contrast enema Rectal disease Congenital abdomen meconium loops Transition zone stimulation/ irrigation central Squirty stool ± air in rectum Rectal biopsy hypo­ on rectal / ventilation exam pull-through

Distal Imperforate anus None VACTERL Distended Yes May pass Multiple grossly Physical exam ± Colostomy/ association abdomen meconium dilated loops ultrasound of anoplasty via No air in perineum or rectum

Courtesy of The Hospital for Sick Children, Toronto, Ontario. and timing of presentation after birth are fundamental to Abdominal Distention the formulation of a diagnosis and the subsequent clinical The degree of abdominal distention depends largely on management (Table 3). the level of obstruction. The more distal the obstruction, the greater the distention. Proximal obstructions, such as duo- Vomiting denal atresia and malrotation, present with minimal epigas- Vomitus in a neonate may be bile stained or not. Non– tric distention, whereas ileal and colonic obstructions present bile-stained vomiting may be (rarely) caused by obstructions with prominent mid- to lower-abdominal distention. proximal to the ampulla of Vater, such as an obstruction at the pylorus or the proximal duodenum. Conversely, bile- Failure to Pass Stool stained (green) vomitus is characteristic of obstructions distal The passage of the first meconium stool normally occurs by to the ampulla of Vater, such as obstructions of the second 24 to 36 hours of life.36 If abdominal distention is associated part of the duodenum, the jejunum, the ileum, and, more with failure to pass stool, distal obstruction (colonic, recto- distally, the colon. Other medical conditions, such as pyloric anal) should be strongly suspected. The passage of stool does stenosis, gastroesophageal reflux, and sepsis, can also cause not rule out more proximal obstruction (e.g., jejunal atresia) vomiting, and these need to be investigated as part of the because the obstruction may have developed after meconium diagnostic workup. had passed distally into the colon. Usually in these situations, no further stool is passed after the initial meconium.50

25 Years N EONATAL N ETWORK 3 1 4 s e p t e m b e r / o c t o b e r 2 0 0 6 , VOL. 25, NO. 5 TABLE 4 n Management of Clinical Presenting Symptoms Rationale Assessment Vital signs Reflect cardiovascular stability, fluid status, pain Abdominal assessment Indicate inflammatory and/or congestive process Color (e.g., erythema, blue, shiny) Size (distended, taut, shiny, scaphoid, measurement of Measure baseline and perform ongoing assessment (q2–4h) for girth) changes Visible/prominent vascular markings Visible bowel loops, peristalsis evident Tenderness Temperature Palpation for masses Palpation of liver/spleen Presence/absence of bowel sounds or flatulence Current weight Enteral intake and output (nasogastric/emesis/stool) Indicate ongoing obstruction, ileus Volume, consistency Presence of blood, bile, feculent material Pain scores Signify damage to intestinal mucosa and peritonitis Intervention Insertion of largest possible nasogastric/orogastric tube Allow for maximal drainage and decompression and decrease restriction of diaphragm Minimize risk of aspiration Vascular access Resuscitate with fluids and electrolytes and administer medications (antibiotics, antacid, inotropes) Fluids and electrolytes according to labs and weight Increase fluid volume because of interrupted intestinal integrity changes Diagnostics/ Primary Investigations Lytes, glucose, complete blood count and differential, gas Assess for acidosis/alkalosis, dehydration, hypo/hyperglycemia Abdominal x-ray (anterior-posterior and lateral) Assess for presence/absence and location of gas, evidence of perforation, detection of strangulation, ischemic disorders Secondary Contrast study (upper GI/contrast enema) Determine patency, size, and caliber of GI tract, identify key landmarks Ultrasound Assess quality of bowel wall Determine anatomic position of organs

Courtesy of The Hospital for Sick Children, Toronto, Ontario.

Management inserted (8–10 French) should be used to provide adequate Managing a baby with suspected intestinal obstruction drainage and decompression of the stomach and to decrease requires focusing primarily on gastric decompression via a restriction of the diaphragm. The efficacy of the decom- naso- or orogastric tube and on maintaining fluid and elec- pression is diminished with distal obstructions, however. trolyte balance. Some infants may present with cardiorespira- Particular attention is required to ensure adequate gastric tory instability, symptoms of sepsis, and pain, necessitating drainage for babies requiring nasal CPAP (continuous posi- additional individualized strategies. This section outlines tive airway pressure). principles of nursing assessment and the rationale for man- The gastric tube must be continually drained using an inter- agement strategies (Table 4). mittent suction device. Flushing the tube with air, saline, or water after checking its position ensures patency. Decreasing the Gastric Decompression risk of emesis and the potential for aspiration is key in prevent- When a bowel obstruction is suspected, the infant is given ing further complications. Accurate measurements of drainage nothing by mouth to limit additional fluid in the GI tract. are necessary to assist with maintaining fluid balance. The largest gastric drainage tube that can be comfortably

25 Years N EONATAL N ETWORK VOL. 25, NO. 5, s e p t e m b e r / o c t o b e r 2 0 0 6 3 1 5 Vascular Access Clinical presentation, age, duration, location, and degree Establishing adequate vascular access is essential for any of obstruction are key factors in the calculation of estimated resuscitative and therapeutic measures to be successful. The fluid and electrolyte requirements. Measuring trends over degree of illness at the time of presentation determines the time is essential because changes in electrolytes also reflect need for central vs peripheral venous access, as well as for arte- fluid balance. Assessing weight, skin turgor, serum electro- rial access. If umbilical lines are used, their positions must be lytes, glucose, acid-base balance, urine output, urine specific monitored frequently because abdominal distention can alter gravity and electrolytes, and renal function helps in estimat- the initial position of the tip of the catheter. It is also crucial ing fluid, electrolyte, and energy needs. to notify the surgeon of the nature of the line (venous or arterial), which may influence the choice for location of the Maintenance of Normal pH Balance abdominal incision. Observation for pH imbalance is essential. Both metabolic acidosis and alkalosis may occur with intestinal obstruction, Maintainance of Fluid and Electrolyte Balance depending on the level of obstruction, duration and volume The fluids lost in vomitus and gastric aspirates are easily of emesis, degree of dehydration, and electrolyte imbalance. quantified, but intraperitoneal, interstitial (“third space”), Upper GI tract obstruction may lead to a loss of chloride intraluminal, and intramural losses from the obstructed in the vomitus, for example, subsequently resulting in hypo- intestine cannot be easily measured. In the circumstance of chloremic metabolic alkalosis.62 Respiratory acidosis may hypovolemic shock, fluid resuscitation with normal saline also occur secondary to sepsis and to the respiratory decom- boluses is essential to maintain blood pressure and adequate pensation that ensues as a result of abdominal distention perfusion to all vital organs.61 and decreased lung volumes from diminished diaphragmatic Regular replacement of the measured or visible gastric excursion. losses with a solution that mirrors the electrolyte content of the gastric losses is vital to maintaining fluid and electro- Antibiotic Prophylaxis lyte balance. Because the interstitial losses and the pockets of The history, sepsis risks (pre- and postnatal), clinical stagnant fluid that may exist along the remainder of the GI presentation, and location of a suspected obstruction often tract cannot be quantified, maintenance fluid volume needs dictate the use of antibiotics. The presence of bowel disten- to be above the norms (by approximately 10–20 percent) pre- tion and the potential for translocation of enteric organisms scribed for full- and preterm neonates.5 into the bloodstream via the portal and mesenteric lymph In general, the suspected site of obstruction may indi- nodes often mandate the use of broad-spectrum antibiotics cate the need for additional fluids and electrolytes. For to provide both aerobic and anaerobic coverage.18 Blood cul- instance, in gastric outlet obstruction, fluid loss is low in tures and assessment of the complete blood count (CBC) and sodium but high in chloride. Obstructions along the duo- differential are included in the investigations for septicemia. denum require higher sodium supplementation because pancreatic and bile secretions contain large concentrations Preparation for Surgery of sodium.5 Obstructions distal to the ligament of Treitz Most infants with congenital bowel obstruction require (i.e., jejunal, ileal, and colonic) often require replacements surgical intervention and therefore preparation for anesthe- similar to the content of lactated Ringer’s solution, which sia and operation. Key factors include a thorough history, contains sodium, chloride, potassium, and bicarbonate.18 documentation of vitamin K administration, blood type, Along with crystalloid solutions, colloids (albumin 5 CBC, and coagulation profiles. Preoperatively, fluid resusci- percent and 25 percent) may be warranted secondary to tation and correction of electrolyte disturbances are essential. the protein losses associated with bowel obstruction. The Recognition that the administration of muscle relaxants and goal of colloid administration is to increase the oncotic anesthesia can cause widespread vasodilation and resultant pressure within the vascular bed. Immediate measurement hypotension necessitates extensive preoperative fluid resusci- of electrolytes is vital when an obstruction is suspected.62 tation. The availability of blood products for intraoperative The common practice of waiting to measure electro- use is also crucial. lytes until the “obligatory” diuresis phase occurs in the newborn infant with suspected intestinal obstruction is Summary unwarranted. Neonatal bowel obstruction is a common disease entity Providing an adequate source of energy is important to seen in the NICU and can present in preterm and full-term maintaining normal glucose homeostasis. A history of dehy- infants. The bedside nurse is frequently the first member of dration and inadequate fluid intake may lead to hypoglyce- the health care team to identify the baby with possible intes- mia. Conversely, the stress response to sepsis and obstruction tinal obstruction, whose most common symptoms include may lead to hyperglycemia. Frequent measurement of serum abdominal distension, vomiting, and/or failure to pass meco- glucose is essential, especially with administration of a higher nium stool. In some circumstances, the possibility of a life- than normal volume of maintenance solutions.63 threatening anomaly must be ruled out on an urgent basis.

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Electrolyte problems in 25(2): 97–100. neonatal surgical patients. Clinics in Perinatology 16(1): 219–232. 50. Lloyd DA, and Kenny SE. 2004. Congenital anomalies. In Pediatric 63. Srinivasan G, et al. 1986. Glucose homeostasis during anesthesia and Gastrointestinal Disease: Pathology-Diagnosis-Management, 4th ed., surgery in infants. Journal of Pediatric Surgery 21(8): 718–721. Walker WA, et al., eds. Toronto: BC Decker, 561–572. 51. Carty H, and Brereton RJ. 1983. The distended neonate. Clinical Radiology 34(4): 367–380. About the Authors Nicole T. de Silva completed her undergraduate and graduate 52. Field S. 1984. Plain films: The acute abdomen. Clinical 13(1): 3–40. studies at the University of Toronto before completing her postgraduate nurse practitioner studies at McMaster University. Nicole has cared 53. Walton M, et al. 1999. The abdomen. In Imaging of the Newborn Baby, Kirpalani H, Mernagh J, and Gill G, eds. Toronto: Churchill Livingstone, for critically ill neonates for 20 years and has held multiple positions of 61–85. responsibility with the NICU at The Hospital for Sick Children. She has 54. Shrake PD, et al. 1991. Radiographic evaluation of suspected small bowel been in her role as clinical nurse specialist–nurse practitioner for over obstruction. The American Journal of Gastroenterology 86(2): 175–178. 12 years and most recently provided care to the general surgical neona- 55. Berrocal T, et al. 1999. Congenital anomalies of the small intestine, tal population for over 4 years. Her clinical and research interests lie colon, and rectum. Radiographics 19(5): 1219–1236. with infants with congenital intestinal anomalies and acquired bowel injury leading to intestinal failure. Nicole has provided extensive edu- cational support to nursing students, nursing staff, medical trainees, and physicians in formal and informal settings. Jennifer A. Young completed undergraduate studies at Queen’s University before moving on to graduate and postgraduate certifi- cate work at the University of Toronto and subsequently McMaster University. She has nursed infants and children for 20 years at The Hospital for Sick Children and for the past 4 years has provided col- laborative, comprehensive care to critically ill newborns in the role of clinical nurse specialist–nurse practitioner for the NICU. Jennifer has a particular interest in the newborn with neonatal bowel or cardiovas- cular disease as well as neonatal pain management. Her greatest daily learning is that which comes from mothering two children. Paul Wales is a staff general surgeon at The Hospital for Sick Children and is an Assistant Professor in the Department of Surgery at the Faculty of Medicine of the University of Toronto. He has a master’s degree in clinical epidemiology and is a clinical scientist in the Research Institute at The Hospital for Sick Children. His clinical and research interests focus on the pediatric medical–surgical management of intes- tinal failure and he is the chair of G.I.F.T. (Group for improvement of Intestinal Function and Treatment). For further information, please contact: Jennifer Young, RN, MN The Hospital for Sick Children 555 University Avenue Toronto, Ontario M5G 1X8 Canada E-mail: [email protected]

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