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 gastrointestinal tract 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 International Journal of Health Sciences and Research (www.ijhsr.org) 256 Vol.10; Issue: 8; August 2020 Ketan Vagholkar. Acute colonic pseudo obstruction 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 neurotransmitter 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 megacolon and colitis. [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. neurotransmitters 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, International Journal of Health Sciences and Research (www.ijhsr.org) 257 Vol.10; Issue: 8; August 2020 Ketan Vagholkar. Acute colonic pseudo obstruction 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 anticholinergics, 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 autonomic nervous system. 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 acetylcholine 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