Segmental dilatation of the colon : Support for a muscle wall etiology

A patient with segmental dilatation of the colon who presented with chronic constipation is reported. A review of previous cases of this rarely reported condition and the typical features of the d isorder is presented. A possible contributing factor to its etiology is proposed on the basis of a pathological ,tppearance of the colonic muscle wall not previously described. C a n J G astro• enterol 1989;3(2):47·49

S EGMENTAL DILATATION OF THE CO lon. in which an isolated dilated segment of colon is found with normal proximal and distal colon, was first described by Swenson and Rach auser in 1959 ( I).Since that time, four further cases h ave been reported (2)(3)(4)(5).The basic clinicoparhological features of this disorder are: lack of radiological mo tility in the saccular segment; normal functioning colon proximal anJ disml ro th e dilatation; obliteratio n of the raenia coli , m arked hypertrophy of rhe ci rcular and longitudinal muscle layers; and the presence of ganglion cells through the distended and undistended colon (3).Such features serve co distingu ish it fro m o the r segmental disorders of the gastrointestinal tract (6.7).A further case of this unusual condition in an adult is reported and a pathological finding nor previo u s ly documented is described.

CASE P RESENTATION
A 19-year-old caucas1an female complaining of uri na ry frequency was found ro have a palpable mass in the left abdomen.On functional e nquiry the patient admmed to recent symptoms of anorexia and lower abdominal cramps The p;i-t1enc also haJ inccrmittcnt diarrhea alternau ng with consripatil)l1 and upper abdominal bloating from childhood , in spite of regu lar use of high fibre diets S he had several congcnnal anomalies ,uggestive of inconti n enta p1gmenta mcluJing a small left breast, a pulmonary systolic murmur, poste rior subcapsular cataracts, eccentric pupils and a history of previous surgery for synJactly Radiographs revealed a moderate thoracolumbar scoliosis with a minor vertebral anomaly ar L 1-U levcl and d isorganization of the upper denture to the right of the mid lin e.
Routi ne blood tests were normal as were serum rhyroid hormone leveb, fol ic acid and urinary porphyrins.Anorectal manometry revt'alcd a norma l reccoanal inhibitory response anJ ganglion cells were p resent and n0rmal on rectal biopsy.The u pper gastromtestinnl rract was normal on barium meal and fol lowthrough examination Barium enema and plain abdomma l x-ray demonstrated marked distension oi the colon prox1-

DISCUSSION
Figure 1) Barium enema and 11lam abdominal x-ruy shou•mg gross colonic distension proximal co ch~ sigmoid colon In their in itia l description of segmental d ilatation of the colon.Swenson and Rathauser ( I ) documented the clin1coparhological fea tu res of th ree patients.Including the p resen t repor t, five cases hrivc si nce been added.Of this total, the re arc a n equal number of ma les and females rangi ng in age from a newborn to 22 years.In all cases, symptoms dace from early infancy and appropriate investigations rule out H irschsprung's disease and id iopath ic megacolon.these being the p redominant conditions mimicking the symptom complex of segmental dila• tation.The ex tent of the d ilatation var• ies from localized ( l.3-5) to extensive (2). a common featu re bei ng that the distal exten t is usually in the region of the sigmoid colon .ma! to th e sigmoid colon ( Figure I ).Colonoscopy showed a normal rectum and sigmoid colon but adequate visualization of the proximal distended segment was impossib le owi ng to large amounts of retai ned stool.Transit studies using or'l.llyingested barium impregnated pellets showed no progression beyond the dilated segment by 120 h .
Despite symptomatic treatmen t for a period of fou r years after in itial p resentation, abdominal pain prog ressively increased.Laparommy was carried out after multiple biopsies d istal to the dilated segment aga in demonstrated normal ganglion ce lls and nerve fibres.At operation, marked en largement of rhe colon was seen from the mid-ascendi ng colon to the lower descendi ng colon (Figu re 2) with a large.fu ll thickness diverricu lum of the wall of the colon just distal to the ju nctional zone.Marked asy m metrical chickening o f the muscular wall of the d ilated segmen t was noted, rhe mesenteric wall was marked ly th ickened and the antimesen teric wa ll was q uite ch in .A subtotal colectomy with ileosigmoid anastomosis was performed.
Histology demonstrated the presence of ganglion cells and a normal myenteric plexus throughout the resected specimen.Disorganization of the muscle layers of both muscularis p ropri a and muscularis m ucosa was present in the dilated segmen t.The muscle coat was thickened and was irregularly and haphazardly distributed without its normal layering into circular and longitudinal elements.This appearance was present th roughout the d ilated segment b u r rhe normal anatomical arrangemen t was seen both proximally and distally.The diverticulu m was seen to be of full thickness with normal muscle layers and ne rve clements.The patie n t's postoperative recovery was uneven tful and sh e remains asymptomatic five years lacer wi th a normal clinical and radiological fo llow-u p.
T he presen t patien t had the clinical and pathological feat u res charactcrisuc of this disorder.Other possib le diagno• ses were ru led out by appropriate tests.As the response to resection of the pathological segment is universally good with no return of symptoms.it is likely that th e ca u se o f the p roblem lies in th~ dilated aspect of the colon .Early reports suggested an underlying neurological dis• order in the affected segment ( 1,2) anJ a vascu lar etiology was considered by Hclikson and colleagues ( 5) due to the presence of an abu ndant tortuous serosal vascu lar patte rn supplied by an Figu re 2) Ex/JO~eJ colon w laparowmy shoH"mg che 11111ctwn between the disral normal colon and chi! dilated 1egmt'nC t!'h1ch 1hou•1 ab.1ence of taenw coli Thecccmn is seen m the lower lefc of the picture and ,hou•, ncmnal mu.1de 1mll l<'1cl1 raenia coli 1•isible enlarged marginal colonic artery in the dilated area, but th ese findings have not been consistent.
A common feature in all reports is that of a colonic muscle wall abn ormality, both macroscopic and microscopic, confined to the dilated segment.Muscle thickening is common to all cases except that of a newborn ( 5) and the absence of taenia coli was seen in two o ther reports (2, 5) as well as the present one.Howeve r. the gross and hi stological appearance in this report show even This report adds further evidence to the concept of an abnormal ity of tht' colonic mu~cle wa ll as being the underlying cause of segmental Jilamti0n of the colon.The present patien t had a number of oth er co ngen ital p roblem~ but there is no evide nce for this condition being part of a rnngenical synJrnme at this time.The importance 0f recognition of thi~ disorder is in its excellent response tn surgical therapy in all age grou ps in which 1t has been encoun te red.