International Journal of Health Sciences and Research Vol.10; Issue: 8; August 2020 Website: www.ijhsr.org Review Article ISSN: 2249-9571

Acute Colonic Pseudo Obstruction

Ketan Vagholkar

Professor, Department of Surgery, D.Y. Patil University School of Medicine, Navi Mumbai-400706.MS. India

ABSTRACT

Acute colonic pseudo obstruction is an abdominal emergency seen in elderly hospitalised patients being treated for major orthopaedic or medical ailments. It has to be differentiated from mechanical obstruction. Identifying and treating medical and metabolic derangements is the first line of treatment. If the patient does not respond then prokinetic medications such as neostigmine should be administered. Colonoscopic decompression and finally surgical intervention are indicated in cases resistant to treatment. The morbidity and mortality associated with these modalities is quite high.

Keywords: Acute colonic pseudo obstruction diagnosis management

INTRODUCTION diameter. Therefore the caecum with a Acute colonic pseudo obstruction larger diameter requires less pressure to (ACPO) is best described as acute colonic increase in size and in wall tension. As the dilatation in the absence of intrinsic colonic wall becomes tensed the chances of mechanical obstruction or any extrinsic ischaemia increases with longitudinal inflammatory process. [1,2] It was described splitting of the colonic wall, herniation of by Sir William Ogilvie in 1948. [3] the mucosa and eventually ischaemia and Subsequently the term “Intestinal pseudo perforation. The colon has both sympathetic obstruction” was proposed by Dudley in and parasympathetic innervation. Vagus 1958. [1] Inconsistency in definition and nerve is the parasympathetic supply to the terminology has led to inconsistency in upper up to the splenic reporting and research on this topic. The flexure. The rest of the gut is supplied by incidence of ACPO is 100 cases per 100000 sacral parasympathetic S2 to S5. The inpatient admissions. [1, 4] Colonic ischaemia proximal colon has a rich sympathetic followed by perforation is seen in 10-20% innervation. The lower six thoracic of patients with ACPO. Whereas the segments supply the sympathetic tone to the mortality associated with perforation is right colon whereas the lumbar segments 1- 45%. [1] The condition is complex with no 3 supply the left colon. The transition zone uniform definitive pathological mechanisms of innervation is the splenic flexure. seen. Sympathetic stimulation results in inhibition Basic structural physiology of colonic of bowel motility and contraction of innervation: sphincters. The caecum is located in the right Normal colonic motor activity is regulated iliac fossa. The caecum and ascending colon at various levels. are larger in diameter and have a thin wall a. Colonic smooth muscle as compared with rest of the colon. b. Pacemaker activity generated by Maximum dilatation in ACPO is seen in the interstitial cells of Cajal (ICC). caecum. This is in conformity with c. Intrinsic control via the enteric nervous Laplace’s law. The intraluminal pressure system (ENS). needed to stretch the wall of the hollow d. Prevertebral and spinal reflex arcs. viscus is inversely proportional to the

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e. Extrinsic modulation by the autonomic of one colonic region may potentiate nervous system and the hormonal dilatation of other regions contributing to system. ACPO. [6] Some researchers have claimed therapeutic success of epidural anaesthesia Aetiology: and splanchnic nerve blocks in a few ACPO commonly affects elderly patients anecdotal case reports supporting this with co morbidities. These include a wide hypothesis. Whether it is due to disruption spectrum of surgical and medical diseases of the efferent limb of these reflex arcs or affecting multiple organ systems. (Table 1) simply reduction in the extrinsic There is a vast array of risk factors involved sympathetic supply of the colon continues to thereby supporting a multifactorial aetiology be a debatable issue. Therefore epidural with a variety of pathways converging to a anaesthesia has been implicated as both a common end point of colonic motor cause and a therapy for ACPO. activity. Intrinsic Colonic dysfunction: Possible causative mechanisms of ACPO: Interstitial cells of Cajal (ICC) are Functional obstruction. the pacemaker responsible for generating Autonomic imbalance is the most electrical slow waves, which are moderated acceptable theory for ACPO. Altered by the ENS resulting in the rhythmic extrinsic regulation of colonic function by contractile activity of the intestine. [7] the sympathetic and parasympathetic Permanent impairment of the ENS, ICC and nervous system is the most commonly myopathy characterizes many forms of suggested mechanism for ACPO. Excess of chronic pseudo obstruction. Few studies sympathetic and parasympathetic tone can demonstrated a reduction and degeneration lead to an atonic segment and functional of enteric ganglion cells in the resected obstruction. Majority of patients with ACPO colon specimens of pseudo obstruction have major illnesses which increase the patients. Whether the histological systemic sympathetic tone contributing to abnormalities represent a cause or effect on autonomic imbalance at the level of the the colonic dilatation and pseudo colon. Initial studies with guanethidine a obstruction is questionable. sympatholytic followed by a Nitric oxide (NO) is an important parasympathomimetic drug triggers colonic inhibitory released by the high amplitude propagating sequences colonic enteric neurons and is implicated in (HAPS). [5] This strongly supports the colonic dilatation and dysfunction in toxic hypothesis of autonomic imbalance as the and . [7] However there is cause for ACPO. no substantial evidence to support the role Colonic Reflex Arc: of NO. PEG (polyethylene glycol) an Several spinal and ganglionic reflex osmotic laxative reduces NO production and arcs are involved in regulating intestinal also reduces the relapse rates after motor activity. Colo-colic inhibitory reflex decompression in ACPO. is inhibition of proximal colonic motor Chronic disease and pharmacologic factors: activity in response to distal colonic ACPO patients are elderly distension. Conversely proximal distension individuals with chronic cardiac, respiratory causes a reduction in basal intraluminal and neurologic diseases such as pressure in the distal colon. Reflex arcs are Parkinsonism. Chronic stress conditioning mediated via afferent mechanoreceptors causes effects of chronic disease. It synapsing with adrenergic efferent neurons potentiates excitatory and inhibitory in the prevertebral ganglia and spinal cord. potentially explaining this These reflexes provide a possible association. mechanism to explain how one region may Effects on ENS and extrinsic regulation are potentiate disordered motility and distension seen in patients suffering from diabetes,

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Parkinson’s disease and Alzheimer’s variety of electrolyte disturbances disease. Effect on ENS and ICC accompany ACPO. These include degeneration with age explains the alterations in Na and K ions. Electrolyte preponderance of elderly population. [7] imbalances have been identified as a Patients with chronic conditions on predictor of poor clinical response to medications: neostigmine. Prostaglandin and cytokine These medications include release can cause acute small intestinal , opiates, calcium channel motility, altered ICC function and slow blockers and psychotropic drugs. wave frequency. Increased expression of Antimotility agents inducing ACPO is a COX 2 is seen in distended colon of mice in predictor of poor response to neostigmine. experimental models. The effect is mediated Management associated with ACPO through PGE2. However similar results are modulate the . not seen in human studies. [9] Clonidine and amitraz are alpha 2 Viral enteroneuropathy: adrenergic agonists. Alpha 2 adrenergic ACPO is associated with viral signalling reduces release of infections. These include herpes zoster from enteric neurons resulting in a relative reactivation involving the lower thoracic imbalance of sympathetic or and lumbar segments, disseminated parasympathetic supply consistent with the varicella zoster, acute cytomegalovirus and current theory regarding the severe dengue infections. The possible pathophysiology of ACPO. [7, 8] explanation is autonomic dysfunction. Obstetric aetiology: Herpes infection affects enteric ganglion The commonest operation leading to thereby leading to sympathetic autonomic ACPO is caesarean section. However it can neuritis causing decrease in sympathetic occur even after normal and instrumental activity. Local segmental colonic vaginal delivery as well. Other causes are inflammation will cause stimulation of the pre-eclampsia, multiple pregnancies, anti- sacral nerve roots leading to blockage of the partum haemorrhage, and placenta previa. colonic parasympathetic supply. Viral Possible mechanisms of ACPO developing spread from the dorsal root ganglion to the after caesarean section are compression of thoracolumbar or sacral columns could parasympathetic plexus by the gravid uterus interrupt the sacral parasympathetic or the fall back of the uterus into the pelvis pathways. Involvement and inflammation of following delivery causing mechanical the intrinsic can also obstruction at the recto sigmoid junction. lead to post viral dysautonomia. [9] Pregnant state causes increase in the Other possible hypothesis which progesterone and glucagon levels. Both have been proposed are compromise in the diminish the tone of the large bowel and blood supply to the colon, “ Hinge-Kinking” predispose to ACPO especially when of the colon at the transition from retro to combined with acute physiologic intraperitoneal junction, air fluid lock disturbances such as surgery, pre-eclampsia, syndrome and colonic distension due to peripartum sepsis or haemorrhage. Resting aerophagy in COPD patients. sympathetic outflow is increased in the third Having reviewed all postulated theories it is trimester even in women with normal blood evident that that the precise mechanism is pressure. Autonomic dysfunction and still unclear. However autonomic imbalance sympathetic over activity are features of seems to be the most accepted hypothesis pre-eclampsia. [1, 6] for the aetiology of ACPO. Metabolic factors: ACPO patients are systemically unwell or Disrupted homeostasis is common in have lesions disrupting the autonomic ACPO. This can precipitate or exacerbate supply of the colon. The transition point for the effects of altered autonomic function. A distended to normal colon in ACPO occurs

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at the splenic flexure corresponding to the parameters will be altered in a select few change in autonomic innervation of the mid patients. gut and hind gut. Physical examination will reveal Clinical presentation: rapidly developing ACPO occurs in debilitated, hospitalised and tenderness. If there is ischaemia or patients who have multiple medical perforation patient will have rebound problems associated with surgical tenderness, guarding or even rigidity conditions. depending on the progression of . The onset of symptoms is insidious, [10] Bowel sounds will be absent or usually 3-5 days postoperatively. hypoactive high pitched in nature. Digital Abdominal pain, and vomiting are examination of the will reveal an seen in 80% of patients. There is history of empty rectum. obstipation and accompanying fever. Vital

Table 1 Risk factors for acute colonic pseudo obstruction. Surgical Cardiac surgery, spine surgery, orthopaedic surgery Neurological Parkinson’s disease, dementia, Alzheimer’s disease Metabolic Electrolyte imbalance, diabetes, renal failure, hepatic failure Medications Opiates, anti-Parkinson drugs, anticholinergics, antipsychotics, clonidine Gynaecologic Caesarean section, instrumental delivery, pregnancy, pelvic surgery Infections Varicella zoster, herpes virus, cytomegalovirus Cardiorespiratory Shock, myocardial infarction, CCF, COPD Other causes Sepsis, major burns, trauma

therapeutic in a few cases. Plain x ray of the abdomen is diagnostic. (Figure 1) The only issue is to rule out a mechanical cause for obstruction. Plain x ray can also help in this respect. The patient can be placed in right lateral decubitus position for several minutes. The gas will pass into the distal colon. Gaseous filling of the rectum can be facilitated by positioning the patient in prone lateral view of the pelvis. This progression of gas in the colon has a 75% success rate in excluding mechanical obstruction and gaseous filling which do not occur in patients with mechanical obstruction. [11, 12] A transverse diameter of the caecum exceeding 12 cms is worrisome and calls for more proactive or aggressive treatment. Abdominal CT scan will be Figure 1: Plain X ray abdomen showing distended colon necessary to exclude mechanical obstruction and . Contrast enema has Investigations: also been suggested. However perforation Complete blood count and renal needs to be ruled out before considering this profile is necessary in all patients. option. Meglumine diatrizoate a water Leucocytosis is seen in most of the patients. soluble contrast is usually used. This has to Serum electrolyte examination is necessary be a low pressure enema where no air in all patients as most of the patients have should be used. The examination is altered levels. Renal insufficiency is also a terminated when the dilated colon is common accompaniment in most patients. reached. Hyperosmolarity results in fluid Correction of metabolic derangements is

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shifts into the lumen which increases which increases the chances of perforation. colonic motility thereby evacuation of air Gas cannot be insufflated in ACPO. from the distended colon. [12] The recurrence rate with colonic Flexible is another decompression is 18-65%. Placement of an diagnostic modality. It is helpful in indwelling colonic tube up to the level of differentiating pseudo obstruction from the transverse colon can help in reducing the mechanical obstruction. It is therapeutic in recurrence rate. Post procedure achieving colonic decompression. If administration of PEG (polyethylene glycol) mechanical obstruction is diagnosed then it helps in reducing the recurrence rate. [11, 12] enables biopsy of the lesion. The only pitfall In patients who were on opiate is that the visibility is poor as prior colonic analgesia and have developed ACPO, preparation cannot be done before the methyl naltrexone a peripherally acting procedure. [12] antagonist is useful if neostigmine fails to relieve ACPO. Other promotility Treatment: agents have been tried such as The priorities in management include erythromycin, cisapride and 1. Exclude mechanical obstruction. metoclopromide. However the results with 2. Aggressive correction of metabolic these medications are not promising. [12, 13] derangements. If all conservative methods fail then surgery 3. Optimization of medical co morbidities. is indicated. [14, 15] A tube cecostomy may be 4. Discontinuation of all potential performed. However the thinning and medications which interfere with friability of the distended caecum can limit motility of the colon. (Anti- a successful outcome in such patients. The parkinsonism medications, calcium next surgical option is subtotal colectomy. channel blockers etc.) However the morbidity and mortality with 5. Nasogastric tube insertion with this procedure is high. [16] continuous aspiration and drainage. 6. Correction of fluid and electrolyte CONCLUSION depletion. Acute colonic pseudo obstruction is Quite a few number of patients will respond rare condition seen in elderly hospitalised to this treatment. patients with an accompanying surgical or If the response is poor then cholinesterase medical disease. Plain X ray abdomen is inhibitors is the next therapeutic option. diagnostic. However mechanical obstruction Neostigmine is the drug of choice. [13] needs to be ruled out by CT scanning. Contraindications to the use of neostigmine Aggressive conservative treatment are including supportive care with correction of Heart rate < 60 beats /minute. metabolic derangements is the first line of Systolic BP < 90 mm of HG treatment. A suboptimal response Acute bronchospasm needing active necessitates the use of other options which treatment. include neostigmine therapy, colonic Neostigmine is administered in the decompression and eventually surgery. dose of 2 to 2.5 mgs intravenously slowly over three minutes. The dose can repeated Conflict of interest: None after 3 to 4 hours. If there is no response to Funding: Nil two successive doses then colonoscopic decompression is attempted. It is effective ACKNOWLEDGEMENTS I would like to thank Parth Vagholkar for his in 85% of cases and can be repeated. It may help in typesetting the manuscript. be technically difficult due to an unprepared colon. The colon in ACPO is papery thin

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