“Marbles of the belly” The Pediatric Spectrum of Cystic Abdominal Lesions Drs. Katie Lopez, Maria D’almeida and Ricardo Restrepo

Take a tour through the different Urinary Tract sections of the abdomen, to see the common and not so common Pancreas, pediatric cystic lesions which arise from various organs. Hepatobiliary Click on the icon to the right to go to each specific section. A main Gynecologic menu icon on each slide (in the top right corner) will take you Non-organ back to this page. based cysts Bladder

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Clinical history: • 10 year old girl with lower abdominal pain. • Differential diagnosis? Bladder

•In both adnexa, are enlarged multi-cystic masses with enhanced through transmission. No normal ovarian tissue was discernible. •Differential diagnosis includes polycystic ovaries, ovarian hyperstimulation syndrome or cystic ovarian tumor. Bilateral serous cystadenomas

Discussion of the differential diagnosis: •In polycystic ovaries (PCOS), the ovaries are enlarged with classically small follicles and cysts (<10mm). Our patient did not have the classic triad of obesity, hirsutism and menstrual abnormalities commonly seen in PCOS. •In ovarian hyperstimulation syndrome (OHSS), the ovaries would have the same appearance, however ascites is commonly seen. Classic OHSS is seen in women of child-bearing age on ovarian stimulating medication (Perganol). •Causes of polycystic ovaries in kids is from unopposed estrogen stimulation, such as genetic deficiencies in certain enzymes, particularly 21-hydroxylase (congenital adrenal hyperplasia). Bilateral ovarian cysts have been observed in older girls with longstanding, untreated hypothyroidism. Bilateral serous cystadenomas

Discussion: •Ovarian neoplasms are not common in children. They are divided into origin of their cellular components: germ cell, sex cord stromal, and surface epithelial. •Only 20% of pediatric ovarian tumors are epithelial, with 80% of those being cystadenomas. Most common tumor is the germ cell (60%) with most of those being teratomas. •Cystadenomas are benign tumors, uncommon before puberty and are usually unilateral. They contain serous or mucinous material. •Classic finding on ultrasound is that of a multiseptated cystic mass. •Our patient remained asymptomatic, however since there was a familial history of ovarian teratoma with torsion, elective laparoscopy was performed. The cysts were enucleated from the ovaries and normal ovarian tissue was salvaged. This is a different patient with a serous cystadenoma. The patient is a 16 year old female with acute abdominal pain and vomiting. The ultrasound was notable for a large intra-abdominal, nonvascular cystic mass of uncertain etiology. A normal right ovary was seen, but not a left ovary. A CT scan was performed. Scout film from the CT scan revealed an abnormal density along the right lower abdomen and pelvis with mass-effect on adjacent bowel. •CT reveals a large cystic mass with a tubular stalk that descends into the pelvis. •The mass appeared pelvic in origin therefore an ovarian cystic lesion was of concern. Serous cystadenoma with torsion

• There was a radiographic and clinical concern for torsion, therefore the patient was taken to the OR. The mass arose from the left ovary and had torsed the ovary and fallopian tube by 720º and had flipped up into the abdomen. The left ovary was not salvageable. • Important teaching point = if you think there could be ovarian torsion, then raise the possibility! Clinical history: •9 year old girl with 2 day history of intermittent abdominal pain with vomiting. •Diagnosis? Findings: •Ultrasound demonstrates a large, avascular cystic mass in the pelvis, slightly right of midline. The mass is adjacent to, but separate from the ovaries. The mass has a well defined wall and contains a few septations or excresences off the wall. •Differential diagnosis: cystic ovarian mass versus a developmental cyst. CT was performed to better evaluate the mass. What is your diagnosis now? Dermoid (cystic teratoma)

CT demonstrates a predominantly cystic mass in the pelvis which contains a focus of fat and calcification. Dermoid Cyst (Mature cystic teratoma)

• Because of the clinical symptoms, associated ovarian torsion could not be excluded. At surgery, the mass had caused torsion, however the ovary was salvageable. • 60% of ovarian tumors in kids are germ cell in origin, of which 70% are teratomas. • The terms “dermoid” and “teratoma” are used interchangeably, however precise definition of dermoid is that it contains two cell layers, while teratoma contains all three (endo-, meso- and ectoderm). • Almost all are benign and 25% are bilateral. • US –2/3rd are complex cystic lesions commonly with echogenic debris or shadowing portions which obscure deeper areas of the mass (“tip of the iceberg” sign). 1/3rd are either predominantly solid or cystic. • CT is good for showing fatty and calcific components. •Clinical history: 16 year old female who presented with 1 week of abdominal pain, no vomiting or fever. The C-reactive protein and white blood cells were elevated, ß-HCG was negative. An ultrasound was ordered. •Findings: A small cyst in the pelvis and enlarged right ovary. Since the labs were notable for infection, a contrasted CT scan was performed. •CT scan demonstrated the same cystic lesion in the pelvis (arrow), however also showed significant inflammatory changes in the region of the right hemi-pelvis, and enlargement of the right ovary compared to the left. The cyst was thought to represent a para-ovarian cyst on the prior ultrasound. •Considerations for the inflammation in the right hemi-pelvis included: pelvic inflammatory disease or possibly ovarian torsion. Cyst of Morgagni with tubal torsion • Since the patient had an acute abdomen, she was taken to the OR. • A 3 cm cyst was seen at the tip of the right fallopian tube resulting in tubal torsion. The ovary however was not torsed. • Cyst of Morgagni is a type of para-ovarian cyst. If the cyst is attached to the fringes of the fallopian tubes, they are referred to as cysts of Morgagni, or Hydatids of Morgagni. • Even though the cyst was very small, it resulted in torsion. Clinical historyBL: BL •Newborn female undergoing an out-patient renal ultrasound to follow-up a prenatal diagnosis of hydronephrosis.

•Upon imaging of the bladder, we noted an adjacent large cystic structure in the pelvis with a fluid-debris level. Differential diagnosis of a complex cystic lesion in the BL pelvis in a neonate: BL • hemorrhagic ovarian or developmental/duplication cyst • dilated fluid filled vagina or uterus seen in hydrocolpos or obstructed uterine horn in a didelphic system. We verified the presence of a normal uterus (seen at left). The location and characteristics were compatible with a hemorrhagic neonatal ovarian cyst. BL NeonatalBL ovarian cyst

• Not uncommonly seen and perhaps due to increased sensitivity to maternal hormones. • The larger cysts are at increased risk for ovarian torsion. It is reported that fluid debris levels and low level echoes suggest torsion. • These can be followed conservatively if smaller, but may need surgical intervention if large. Clinical history: •17 year old sexually active female with 5 day history of abdominal pain and fever. White blood cell count is elevated. •Diagnosis?

BL BL

Right Left bladder Clinical history: •The ultrasound demonstrated dilated, cystic tubular structures, with some internal debris, on both sides of the pelvis. No normal Right ovarian tissue was seen. •The differential diagnosis includes hydrosalpinx, pyosalpinx, or tubo-ovarian abscesses (TOA). •Patient also had a CT scan for further evaluation.

Left •The CT scan also demonstrated dilated, cystic tubular structures with enhancing walls in the region of both adnexa with continued differential of hydrosalpinx, pyosalpinx or bilateral TOAs. •Pyosalpinx or TOA was of more concern due to fever and abnormal labs. •As the patient had persistent abdominal pain and fever refractory to medical management, she was taken to the OR for exploration. Bilateral Tubo-ovarian abscesses

• At surgery, both fallopian tubes were aspirated with the removal of copious amounts of frank pus. There were innumerable adhesions in the pelvis as well. This suggests pelvic inflammatory disease resulting in tubo-ovarian abscess (TOA). • TOAs result from pelvic inflammatory disease with extension of infection into the tubes AND ovaries. • Tends to be bilateral. • US is unreliable in distinguishing pyosalpinx from hydrosalpinx, as echoless fluid can be infected and echogenic fluid is not always infected. • Most common US finding in TOA, is partial or complete replacement of the normal ovarian tissue by a heterogeneous mass or a hypoechoic area with contained debris. Clinical history: •37 weeker born with hydrops and common urogenital sinus. •Prenatal ultrasound was notable for bilateral hydronephrosis and distended bladder. •This newborn underwent ultrasound of the kidneys and bladder to follow-up the prenatal findings. •Can you see the abnormality on this plain film? Did you notice the abnormal density in the lower abdomen/pelvis with displacement of bowel loops? •The ultrasound shows a cystic mass posterior to the decompressed bladder which contains a foley balloon (arrow). There is a large amount of debris within the mass. •Differential diagnosis includes: hemorrhagic neonatal ovarian or developmental/duplication cyst. •The key point in these cases is to always look for the uterus, so you don’t get fooled into calling an ovarian cyst when the other possibility is an obstructed vagina or uterus in either hydrocolpos/hematocolpos or obstructed uterine horn in a didelphic system. Further evaluation demonstrated the large cystic mass to represent an obstructed, debris filled vagina, which you can see attaches to a mildly distended endometrial canal of the uterus (arrow). MRI was performed to better delineate the anatomy. T2 sagittal images demonstrate a markedly dilated vagina which is blind ending in the pelvis. This represents hydrocolpos/hematocolpos. The make-up of the fluid in the vagina determines whether this is hydro- (simple fluid) or hematocolpos (blood). Hydrocolpos/Hematocolpos

•A congenital obstruction - either persistent urogenital sinus or cloacal malformation in the neonate. If diagnosed in the older child/adolescent then secondary to imperforate hymen, segmental vaginal atresia or transverse vaginal septum. • Rare to present in the newborn period, more commonly diagnosed during adolescence. • If uterus is distended as well, then called hydro-/hematometrocolpos. • Echogenic debris is mucus secretions secondary to stimulation by maternal estrogens in utero. In older patients, the debris represents blood products and sloughed endometrial lining. • Key point! – urinary and gynecologic malformations are associated, therefore always inspect the other system when you find an abnormality in one. Companion case - Clinical history: 16 year old female with spina bifida, augmented neurogenic bladder and ventriculoperitoneal shunt, presents with increasing abdominal size. Patient has never had a normal menstruation. She had occasional irregular periods with scant blood only. BL

Findings: There is a large echogenic mass in the abdomen, extending from the epigastrum into the pelvis. The mass has a thick wall and what appears to be layering debris (arrow). The bladder (BL) is separate from the mass. The mass has a bilobed appearance with a smaller portion of the mass in the epigastrum which has a connection (thin arrow) to the larger mass. Doppler imaging revealed no hypervascularity. Diagnosis? •The findings, along with the clinical history, are consistent with hematometrocolpos. •MRI was performed. T2 weighted oblique coronal and sagittal images are consistent with this diagnosis. The vagina is markedly distended with a rounded inferior aspect. At surgery the patient was noted to have a transverse vaginal septum. The smaller uterus has a fluid-debris level of differing blood products. This is a recent companion case of hematometrocolpos. This 15 year old girl has never had a menstrual period and now presents to the emergency department for worsening pelvic pain. The ultrasound findings and clinical history are classic. Clinical history: This is a 13 year old female who presented with acute urinary retention. Prior history includes normal menses. A renal ultrasound was initially performed (not shown), which noted a solitary large left kidney and this large cystic mass for which MRI was performed for further evaluation. The bladder was seen separately.

Thank you to Dr. Luisa Cervantes, from Miami Children’s Hospital, for this case. bladder

sag coronal

The sagittal T2 demonstrates a large cystic mass which extends deep into the pelvis with a blunted inferior end. The coronal view shows that the cystic mass communicates with the right horn of a didelphic uterus (arrow). •Axial images demonstrate the didelphic uterus and the connection of the mass with the right sided horn (arrow). Also note on the image to the lower left, there is a compressed structure directly to the left of the cystic mass (arrow head). This has a very dark signal intensity outer lining with bright internal signal. This represents the vagina connected to the left sided horn. •Therefore this is a didelphic uterus with a unilateral hydrocolpos. Uterus didelphys with unilateral hydrocolpos

• This is a total failure of müllerian duct fusion. Complete duplication involves 2 vaginas, 2 cervices and 2 uterine horns. • May be associated with renal agenesis. Our patient did have an absent right kidney. • Hydrocolpos was due to a transverse vaginal septum. Right lower quadrant

Clinical history: •4 month old male with a palpable right inguinal mass. •Diagnostic considerations include patent processus vaginalis, inguinal hernia and spermatic cord hydrocele. Diagnosis: Spermatic cord hydrocele •This is a cystic mass in the inguinal canal with blunted proximal and distal ends. The distal end is near the superior scrotum and does not communicate with the scrotal cavity. The proximal end is also blunted and does not communicate with the peritoneal cavity. Valsalva manuever does not change the appearance of the mass. A single septation inferiorly is seen. Spermatic cord hydrocele

• Uncommon congenital anomaly. • Results from abnormal closure of the processus vaginalis. • Presentation is usually as firm groin swelling. • Ultrasound appearance classically shows an anechoic lesion in the inguinal canal which does not communicate with either the peritoneal or scrotal cavities. Septations can be seen. • Must distinguish from inguinal hernia. There should be no bowel within the canal and no opening of the internal inguinal ring suggesting communication with the peritoneum. Different patient: •4 year old with persistent right inguinal mass, that did not change with valsalva or communicate with the scrotal or peritoneal cavities.

•Again note the blunted proximal and distal ends, as seen in our last case. This spermatic cord cyst is more simple in appearance. End of this section

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To proceed to the next section, Pancreas and Hepatobiliary, press the spacebar or enter •7 year old boy who was in a scooter accident in which the handlebars hit the child in the abdomen. •What is the diagnosis and complications? Pancreatic laceration

•Did you see the linear area of low density near the pancreatic neck and small peripancreatic fluid? •This represents a pancreatic laceration. •A common presentation of this injury, just like our child, involves the child falling onto handlebars of a bicycle. •If there is a ductal injury, then complications are worse and include: recurrent pancreatitis, pseudocyst, pseudoaneurysm, fistula and abscess Same case. Our child had increasing abdominal pain, so a repeat CT scan was performed. Do you see the abnormality on the scout film? There is mass-effect on the stomach and nasogastric tube, resulting in deviation of these structures to the right. Diagnosis? •Axial images reveal a fluid collection in the left upper quadrant. On the 1st image, you could be fooled into thinking this was the stomach, however note the position of the NG tube, which does not go through the fluid collection. •The stomach and NG tube are compressed by the cystic lesion. •Where does it arise from? Note the close apposition of the lesion with the pancreas. Pancreatic pseudocyst

• Collection of pancreatic fluid encapsulated by fibrous tissue. • Requires >4 weeks to form and matures in 6-8 weeks. • Usually is in the region of the pancreas, however can be in the mediastinum or anywhere in the abdomen. • Most resolve spontaneously. • Well evaluated with US or CT. • Indications for drainage: pain, suspected infection, persistence of >5cm in size, increasing size, biliary/GI obstruction. Clinical history: •12 year old female with blunt abdominal trauma. •Diagnosis? A post-traumatic hematoma, right? Not necessarily! Let’s look at the images carefully. •On this first image, there is a heterogeneous mass with areas of low density (possibly fluid) and areas of higher density (blood or solid material). You can see the splenic vein (arrow). Note that the mass is adjacent to the splenic vein, in the expected location of where a normal pancreas should be. •On this image, you can see a head and uncinate process of the pancreas. Where is the body? Also, note that the head of the pancreas makes a “claw” sign (arrow) with the mass (the pancreas wraps around a portion of the mass). • With the history of blunt abdominal trauma, duodenal hematoma should always be considered. This image shows that the horizontal portion of the duodenum is adjacent to the mass. Therefore, could this be a duodenal hematoma? •Since there was a history of trauma, we could not exclude that this was a duodenal or mesenteric hemorrhage, however with it’s mass-like appearance, we recommended a follow up to insure resolution. •The lesion did not resolve or change on a follow-up US, therefore the patient was taken to the OR for exploration. Papillary cystic tumor of the Pancreas

• Not all trauma is bad. Because of the blunt trauma, we were able to identify the tumor in this patient who was previously asymptomatic. • Pancreatic tumors are very rare in childhood. • Tumors may arise from the islet cells (insulinoma, gastrinoma), exocrine tissue (cystadenoma, adenocarcinoma) or acinar cells (pancreaticoblastoma). • Our patient’s tumor is a rare, low grade malignant tumor. • Commonly described as a well-encapsulated mass with considerable hemorrhage and cystic degeneration. • Most frequently in the tail of the pancreas. • Prognosis is excellent after excision. Only 4 % present with metastases. •Clinical History: Full-term 6 month old female presenting with jaundice and increasing abdominal distention for 1 month •Labs:elevated direct and indirect bilirubin, ALT/AST, alkaline phosphatase, WBC count Differential Diagnosis?

• As this appears to involve the biliary tree, there really is no differential, likely a choledochal cyst. • What test would you do next and why? The next test was a nuclear medicine biliary scintigraphy. This test will prove if the cystic structure connects with the biliary tree as it fills with radiotracer. Our study showed no excretion by the liver due to severe dysfunction. Now what study would you do? •Our patient was taken to the OR for an intraoperative cholangiogram. •The choledochal cyst was percutaneously studied and showed no excretion from the cyst into the duodenum, therefore it was obstructed. •The patient underwent cyst removal and Roux-n- Y hepaticojejunostomy Choledochal cyst

• Definition: refers to dilatation of the common bile duct which can be either fusiform or saccular. • Classification scheme - most commonly used is the Todani et al. – with 5 types. • 80-90% are the Type I – dilatation of the common bile duct (CBD) over a variable length (our patient had this type). • Pathogenesis - current theory is anomalous insertion of the pancreatic duct into the CBD with reflux of pancreatic enzymes resulting in inflammation and obstruction. • Radiology – US and radionuclide studies usually suggest the correct diagnosis. • Complications – ascending cholangitis, cirrhosis, 20-fold increased risk of carcinoma of the biliary tree, spontaneous cyst rupture. Is this another choledochal cyst?

Clinical History: • 4 year old presenting with 1 week of crampy, intermittent abdominal pain and vomiting. • Patient was found to have an intussusception which was reduced. Patient was admitted for observation, and admission labs revealed elevated liver function tests and bilirubin levels. Ultrasound was initially performed which then prompted this MRCP. •The cause of the biliary dilatation is the large filling defect in the distal common bile duct. This represented a large stone. •The stone is well seen on these axial T2 images. Obstructing CBD stone

• Cholelithiasis in children is uncommon. Causes include: total parenteral nutrition, diuretics, dehydration, infections, hemolytic anemia, kids with short gut syndrome, inflammatory bowel or cystic fibrosis, patients with congenital abnormalities of the biliary tree, antibiotics and idiopathic.

• Ultrasound is a first line diagnostic tool, however MRCP is more sensitive for evaluating the entire biliary tree and to localize the obstructing stone. Clinical history: The patient presented with a fever of unknown origin. The chest x-ray was notable for a subpulmonic effusion which prompted evaluation for a possible liver abnormality. •CT scan demonstrates a slightly irregular, intrahepatic cystic lesion with a thick, enhancing wall.

•Infection or tumor? •As far as tumors go… •Hemangioma? – this doesn’t have the typical peripheral nodular enhancement. •Hemangioendothelioma – could have this appearance, but seen in kids < 6 months. •Mesenchymal hamartoma – this benign liver lesion is commonly multilocular. •Hepatoblastoma – patient should be less than 3 years old and these usually have a more solid appearance (as does hepatocellular carcinoma). •Solitary metastasis – not likely. •Infection or tumor? •As far as infection goes… •Pyogenic abscess – would look like this, however more commonly is seen in the immunocompromised which our patient was not. •Fungus and cat-scratch infection – more commonly multiple small, ill-defined, hypodense nodules. •Parasitic infection: •Echinococchal – can be simple appearing, however also known to have multiple daughter cysts and commonly wall calcifications. •Amebic – unilocular, solitary, usually in the right lobe of the liver and commonly have a peripheral hypoechoic “halo” around the lesion (edema). Hepatic amebic abscess

• The radiographic findings fit the pathologic diagnosis, as the lesion is a solitary, unilocular, hypodense lesion with a peripheral “halo” of edema. • Caused by the parasite Entamoeba histolytica. • Infection is via the intestines with the liver secondarily infected via spread through the portal vein. • More common in kids under 3 years of age. • Ultrasound is usually diagnostic. Clinical history: Adolescent male from India who presented with abdominal pain. Diagnosis? Echinococcal cyst

• Also known as hydatid disease. • Infestation by the larval state of the Echinococcus tapeworm. • The pathologic findings explain the imaging findings. – There are 3 layers surrounding clear fluid. There is a rigid outer layer, a middle acellular layer and a thin inner layer in which the daughter cysts arise. • Therefore, the split wall appearance is the inner wall detaching from the middle layer. • CT may also show daughter cysts and wall calcifications. • Treatment can now be done with medical therapy, surgical removal or percutaneous drainage. Clinical history: 3 year old boy presented with palpable abdominal mass.

Differential diagnosis? Findings: •There is a well defined cystic mass with thin septations and no significant enhancement or calcifications are seen. This is within the liver as you can see a thin rim of normal liver tissue that surrounds the lateral border of the lesion. •This has a nonaggressive appearance and may represent a multilocular cystic mass of mesenchymal hamartoma or possibly hydatid disease with multiple daughter cysts. Mesenchymal hamartoma

• Account for nearly ¼ of benign liver tumors in childhood. • Presents in kids less than 2 years of age, with an asymptomatic abdominal mass. • US or CT demonstrates a multi-septated cystic mass, more commonly in the right lobe. The noncystic portions will enhance with intravenous contrast material. • There is documented transformation of this benign tumor into its malignant counterpart, undifferentiated embryonal sarcoma, however some still advocate conservative treatment. Surgical removal is the norm. End of this section

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To proceed to the next section, Non-organ based peritoneal cysts, press the spacebar or enter Clinical history: •Teenager presenting with right lower quadrant pain and fever. •Diagnosis? Plain film demonstrated classic findings of air-fluid levels with a mottled appearance, and a calcification in the right lower quadrant representing appendicitis with abscess formation – well seen on the above CT scan. Different patient: CT shows inflamed appendix with appendicolith and adjacent free fluid. CT 8 days later – development of intra-abdominal abscess. Appendicitis with abscess formation • At our institution, the first exam is ultrasound, and should be in the pediatric patient. • US criteria – non-compressible, blind-ending structure, >6mm in diameter, +/- hyperemia. • US findings suggesting perforation/abscess – periappendiceal or intraperitoneal fluid, mass of mixed echogenicity. • If US non-diagnostic or patient is very large, then a CT scan with intravenous contrast only is performed at our institution. • CT criteria – enhancing appendiceal wall, diameter >8mm. • Plain film findings – splinting resulting in scoliosis with the concavity toward the side of pain, focal ileus/dilated right lower quadrant (RLQ) loop, air-fluid level or mottled appearance in the RLQ if an abscess has formed, distal small bowel obstruction, appendicolith. •Clinical information: 3 month old female with cystic abdominal mass seen on prenatal ultrasound, patient is asymptomatic. • What is your differential diagnosis? •Description: anechoic mass with enhanced through transmission and well defined hyperechoic wall, doppler imaging (not shown) demonstrated no vascularity. •The lesion was adjacent to bowel and did not seem to arise from a solid organ. Differential diagnosis of a cystic mass in the right upper quadrant in an infant • types of developmental/mesenteric cysts: • lymphangioma, enteric, mesothelial, duplication or nonpancreatic pseudocysts •meconium pseudocyst •choledochal cyst •adrenal hemorrhage Duplication cyst

• Developmental cysts that, by definition, contain mucosal and muscular layers. • The majority do NOT communicate with the bowel lumen. • Most frequent location is the terminal ileum or ileocecal valve. • Patient can present with bowel obstruction, peptic disease or GI bleed (if cyst contains gastric mucosa), intussusception and volvulus. • US – anechoic cyst, +/- echogenic debris - if there is an echogenic layer (mucosa) surrounded by a thin hypoechoic halo (representing the muscular layer) = “gut signature,” this can suggest the diagnosis. • Cysts containing gastric mucosa can be identified on technetium-99m pertechnatate scintingraphy, and can be a cause of a false-positive study for a Meckel’s diverticulum. This is another case of a duplication cyst with the typical “gut signature” on ultrasound. The Meckel’s scan was also positive (focus of activity in the right lower quadrant). A duplication cyst which contains gastric mucosa, is a not uncommon false positive on a nuclear medicine study for Meckel’s diverticulum. •CT scans from two different patients - both demonstrate cystic lesions with enhancing walls, characteristic of duplication cysts. •CT is not commonly indicated in the diagnostic work-up. Can you put these findings together to tell the clinical story and explain what these cystic lesions are? What is that catheter? Did you notice the completely calcified native right kidney and an atrophic left native kidney? Clinical history: •15 year old with end stage renal disease secondary to congenital nephrotic syndrome. Patient is status post failed renal transplant, and is now on hemodialysis due to transplant failure. The catheter was a transhepatic dialysis catheter. These large cystic masses represent loculated ascites. Clinical history: Teenager with right lower quadrant pain. No fever or elevated white blood cells. There is a nonenhancing cystic lesion in the right lower quadrant that does not have a well-defined wall or adjacent inflammation. The differential is long and includes duplication cyst, mesenteric cyst, lymphangioma, or possibly a cyst related to the ovaries. Mucocele of the Appendix

• This was only diagnosed with pathology. • Mucocele = distension of the appendix with sterile mucus. • Multiple theories on the etiology: cystic dilatation of the lumen by obstruction, mucosal hyperplasia, mucinous cystadenoma /adenocarcinoma, accumulation of thick mucus in cystic fibrosis. • Incidence – 0.07-0.3% of appendectomy specimens. • Common to see rim calcifications. • Not common in the pediatric age group. • CT – round, sharply defined paracecal mass with homogeneous decreased attenuation. Clinical history: •5 year old boy with progressive abdominal distension over many years. He presented to the emergency department with colicky abdominal pain. The patient has no significant past medical history. •Do you see an abnormality on this supine abdominal radiograph? Findings: There is abnormal mass effect with displacement of loops of bowel into the right upper quadrant. Sagittal panoramic view

•An ultrasound was initially performed that demonstrated a large cystic lesion that fills the entire abdomen, extending down into the pelvis, to just above the bladder. The lesion was avascular and contained some echogenic debris. •A CT scan was also performed which noted a large, non-enhancing simple cystic lesion which fills the entire abdomen. The bottom left image demonstrates that the lesion does not arise from any of the major abdominal organs. Mesenteric Lymphangioma

• The patient went to surgery and a massive cystic mass was removed which arose from the mesentery. Chylous fluid was aspirated. • Pathologic diagnosis: lymphangioma. • These are congenital malformations of lymphatic vessels. • They are lined by endothelium only, are commonly multi-septated and may contain chyle. The septations are best seen with ultrasound (see image on the right). • Commonly presents as painless abdominal distension with a palpable mass. Clinical history: 1 month old baby girl who was seen by her pediatrician for vomiting, decreased appetite and crying. On physical examination, the infant would cry when the abdomen was palpated. Patient was sent to the emergency department for evaluation.

•Ultrasound noted a nonvascular, complex cystic mass in the right lower quadrant, with septations and echogenic debris layering posteriorly. •Differential diagnosis? •A complex mass in the pelvis of a female infant who is symptomatic with presumed abdominal pain due to crying on palpation of the abdomen, should raise a red flag to the radiologist, that there is either torsion of the cystic mass or the lesion has bleed or become infected. • Since the mass is in the right lower quadrant, our primary consideration was a right ovarian cyst with torsion. Other developmental cysts that have torsed or become complicated were also a consideration. Omental cyst with torsion

• Omental cyst and mesenteric cyst are used interchangeably. • Different types of mesenteric cysts include lymphangioma, nonpancreatic pseudocyst, duplication cyst, enteric cyst and mesothelial cyst. • Histologic evaluation will usually distinguish the subtypes. • These are developmental cysts resulting from failure of mesothelial peritoneal surfaces to coalesce. • Unilocular, thin-walled, and can contain, serous, chylous or hemorrhagic fluid. • Torsion, hemorrhage and bowel obstruction are complications. • Best evaluated with ultrasound, however determining the subtype of mesenteric cyst is best done with histology. Clinical history: •17 year old boy with a ventriculoperitoneal (VP) shunt for hydrocephalus, now presents with increasing abdominal fullness and pain. •Do you see the abnormality on this scout film from the CT scan? The VP shunt has already been externalized (arrow). There is abnormal mass effect on the bowel which is displaced laterally (arrowheads). Ultrasound was performed. In kids with VP shunts, always look at the distal end of the shunt to look for loculated fluid collections around the tip (CSF pseudocyst/ “CSFoma”). As you can see, there is a large fluid collection around the distal tip of the catheter (arrow), which appears loculated. The CT scan also demonstrates the loculated fluid collection in the mid-abdomen. Some abdominal fluid in kids with VP shunts is normal, however the fluid should be freely flowing and disperse in gravity dependent areas, and not appear as a well-defined loculated fluid collection. Note the VP shunt (arrows) has already been externalized because there was a concern for infection of the fluid. See the nice correlation between the scout film and the coronal reformation from the CT scan. CSF pseudocyst / CSFoma

• There are many common complications related to ventriculoperitoneal shunts: malfunction (mechanical or occlusion), infection, CSF loculation, visceral perforation and shunt migration. • CSF pseudocysts form when adhesions develop around the tip of the shunt tubing with eventual encapsulation of fluid and obstruction of the shunt. • Ultrasound is the most common study for diagnosis. The shunt tubing has a characteristic appearance of several parallel echogenic lines. This is a different patient with a complex CSFoma – note the thickened wall and septations. The echogenic lines are the tip of the VP shunt (arrow). Clinical history: • Adolescent male with trauma to the abdomen after falling off a bicycle and onto the handlebars. • Diagnosis? Duodenal hematoma

• This is a classic appearance of a large duodenal hematoma which appears as a dumb-bell shaped cystic lesion along the expected course of the horizontal duodenum. • This is the region of duodenum that is most commonly injured. A blunt abdominal injury results in compression of the horizontal portion against the spine. •The hemorrhage is intramural in location, typically through a partial-thickness tear. • Usually managed non-operatively. • CT appearances include focal bowel wall thickening or this dumb-bell shaped lesion in large hematomas. • Can be evaluated with fluoroscopic barium exam, ultrasound or CT. End of this section

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To proceed to the next section, Urinary tract, press the spacebar or enter Clinical history: •13 month old female with fever, abdominal pain and focal redness along the anterior bladder abdominal wall. Sag bladder•Ultrasound noted a complex cystic mass directly superior to the bladder, along the midline anterior peritoneum. The cyst contained echogenic material/debris. •Diagnosis? Sagittal - contrast filled bladder

•A contrasted CT scan was also performed as the etiology of the mass was uncertain. •CT noted a cystic mass with a thick enhancing wall just superior to the bladder, extending along the anterior abdominal wall. The key finding is that this entends from the dome of the bladder into the region of the umbilicus. Infected Urachal cyst

• Urachal remnants result from failure of the urachus (median umbilical ligament) to regress. The urachus is the channel between the bladder and the embryonic allantois. • This can be open anywhere along the tract from the bladder to the umbilicus. A patent urachus if the entire tract is open, urachal sinus if the proximal portion is open and communicates with the umbilicus, urachal diverticulum if the distal portion near the bladder is open (and communicates with the bladder). The urachal cyst (the most common type) is a patency along the midportion. • These are frequently isolated lesions, however are not uncommonly seen in prune-belly syndrome. • Complications include infection and development of malignant lesions (most commonly adenocarcinoma). • Evaluation is best done with ultrasound, voiding cystogram or direct fistula study with fluoroscopy. Clinical history: 2 month old female with decreased urine output and left flank swelling. Previously treated for UTI. The CT demonstrates a duplicated left kidney with obstructed upper pole moiety and pararenal fluid collection. This was thought to represent a urinoma, which was verified by nuclear scintigraphy (see next slide). The nuclear medicine renogram, in the posterior projection, demonstrates uptake and excretion of radiotracer by both kidneys. Note that there is a focus of activity along the lateral upper border of the left kidney that slowly forms and is best seen around slide #6. This area is persistent even after radiotracer has washed out of the kidneys on the later portion of the exam. Duplicated kidney with urinoma

• Duplication of the kidney is one of the most common anomalies of the urinary tract. There is a wide spectrum of partial and complete duplication anomalies, that should be very familiar to the pediatric radiologist. • The Weigert-Meyer rule refers to the insertion of the ureters of a duplicated system. The ureter to the upper pole moiety inserts inferior and medial to the ureter of the lower pole moiety, which inserts normally. The ureter of the upper pole tends to obstruct (usually by an ectopic ureterocele), and there is reflux into the lower pole moiety. •A urinoma is a result of acute or chronic obstruction or trauma to the intrarenal collecting system, resulting in forniceal rupture. This is another case of a duplicated kidney, with marked obstruction and dilatation of the upper pole moiety and its ureter, by a large ureterocele. Selected images from this patient’s nuclear medicine renogram demonstrate a photopenic defect (arrow) in the upper pole of the right kidney, representing a completely non-functioning obstructed upper pole moiety. This is the second most common cause of an abdominal mass in the neonate, after hydronephrosis (usually from a ureteropelvic junction obstruction). Diagnosis? The ultrasound shows multiple cysts, of varying sizes, in the left renal fossa. The key is that these cysts do NOT communicate (to help differentiate from severe hydronephrosis). There is no normal intervening renal parenchyma. This is a classic appearance for multicystic dysplastic kidney (MCDK). •This nuclear medicine renogram from a different patient, shows the classic appearance of an MCDK on scintigraphy. By definition, there is NO function, so there will be no uptake of radiotracer by the involved kidney. Time-activity curves will obviously be abnormal. •Most commonly MCDK is unilateral, however in 20-30% of cases, there is an associated anomaly of the contralateral kidney! This is another appearance of a right multicystic dyplastic kidney. This is one of the 20-30% of patients with contralateral abnormalities: in this case, moderate hydronephrosis due to vesicoureteral reflux. Clinical history: Child presented with trauma, status post motor vehicle collision. No past medical history. •In contradistinction to the last case, the large cysts involving this kidney do connect. •CT is notable for a markedly dilated renal pelvis, to a greater degree than the calyces. There is a rounded appearance to the pelvis as well. This is a typical appearance for a ureteropelvic junction obstruction (UPJ). As there was an initial obstruction, the subsequent trauma to the abdomen resulted in an acquired urinoma, presumably from forniceal rupture. UPJ obstruction

• The most common cause of an abdominal mass in a neonate. • More commonly seen in boys and on the left side. • Bilateral in 10-20% of cases and up to 30% are associated with other renal anomalies. • Ultrasound is the diagnostic study of choice. Nuclear medicine renogram is useful to evaluate for function. Here is another interesting cause of an acquired cystic lesion (urinoma) in the abdomen. Clinical history: Teenager who presented with trauma (thrown from a snowmobile). The contrasted CT scan demonstrates a horseshoe kidney, which due to the blunt abdominal trauma, resulted in a complete laceration through the mid-portion with a large urinoma. bladder

Clinical history: 11 month old boy with urinary tract infection. •Sonographic images of the bladder in the sagittal plane, demonstrate a cystic lesion at the right posterolateral base of the bladder that changes shape with voiding. •Diagnosis? What test would you perform next? Early bladder filling The two upper images demonstrate focal outpouching of contrast along the posterior inferior right side of the bladder during early bladder filling. This represents a large bladder diverticulum near the right ureterovesicular junction (UVJ).

Post-void The voiding and post-void images to the left, demonstrate a smaller diverticulum in the region of the left UVJ. The larger diverticulum decompresses nicely after voiding. Bilateral Hutch diverticula

• These are “pseudodiverticula” – localized outpouchings of the mucosa between detrussor muscle fibers. These can be congenital or acquired. • The Hutch type is a common primary paraureteral diverticulum, located laterally and cephalad to the ureteral orifice. • Vesicoureteral reflux is present in about half of the cases. • Diverticula are best seen during voiding when bladder contractions force urine into the diverticulum. Clinical history: 2 year old who presented with palpable abdominal mass. The axial image to the left is non-contrast, and demonstrates a large low density/cystic mass in the region of the right renal fossa. Faint calcifications are seen.

The axial image to the right is post-contrast. The mass has minimal peripheral enhancement. Note the “claw” sign of the kidney, which appears to wrap around the mass (arrows), suggesting the lesion arises from the kidney. Wilms tumor

•The most common abdominal malignancy of childhood. • Usually presents as a palpable mass in a toddler. • Children at increased risk include those with nephroblastomatosis, syndromic kids including Beckwith-Wiedemann, Drash and WAGR syndrome, and kids with sporadic aniridia or hemihypertrophy. • Radiologic evaluation, commonly with CT, is focused on identifying the sites of involvement, extension and metastases in order to assist in surgical planning. • CT characteristics: well-circumscribed, heterogeneous partially cystic mass, may contain fat or calcifications, enhances to a lesser degree than the renal parenchyma. Look for nodal or hepatic metastases, tumor extension into the IVC or renal vein and contralateral tumors. Clincial information: •14 year old boy with 2 weeks of worsening left upper quadrant sharp, intermittent pain. •Diagnosis? Diagnosis: Renal abscess •There is a complex, multi-septated cystic intrarenal lesion with enhancing walls and inflammatory change in the perirenal fat, with an adjacent abscess anterior to the kidney. Renal abscess

• The patient failed medical treatment so both abscesses were drained separately. Culture was positive for Proteus mirabilis. • Abscess is a rare complication of pyelonephritis. • More often seen in immunocompromised, or kids with diabetes or sickle cell disease. • US – hypoechoic mass with good through transmission, wall will thicken as the process progresses. • CT – low density lesion, +/- enhancing wall, different from focal pyelonephritis in that they are not wedge shaped. • Differential diagnosis would be a cystic Wilm’s tumor. End of this section

To return to the main menu References

Caffey’s Pediatric Diagnostic Imaging, 10th edition, Kuhn et al., 2004. Pediatric Sonography, 3rd edition, Siegel, M., 2002. Radiology Review Manual, 5th edition, Dähnert, W., 2003.