idiopathic megacolon is a rare and poorly understood clinical condition that usually presents as refractory abdominal distension and constipation . it includes idiopathic megarectum , idiopathic megacolon , or a combination of these disorders . among them , idiopathic megacolon without megarectum is the most uncommon disorder . in this case , we experienced the idiopathic megacolon with bowel dilatation only proximal to the splenic flexure . one month before being referred to our hospital , abdominal distension and constipation developed and the severity of both increased with time . the patient could not defecate and the abdominal pain increased despite fasting and frequent enemas . because of the intractable symptoms , she was referred to our emergency unit for further investigation . the physical examination during the obstructive episodes revealed marked abdominal distension with hypoactive bowel sounds . the patient denied a history of metabolic , neurological , cardiovascular or pulmonary disease , previous abdominal or pelvic surgery , or a history of abdominal cancer , inflammatory disease or trauma . the laboratory testing showed a normal hemoglobin , hematocrit , white blood cell count , blood glucose , creatinine , and coagulation profile . the serum electrolytes were also normal except hypokalemia was present with a level of 2.7 mmol / l ( normal range 3.5 - 5.1 the abdominal computed tomography ( ct ) scan showed bowel distension , and the transition zone was detected at the splenic flexure ( fig . anorectal manometry showed a normal resting anal sphincter pressure , normal squeezing pressure during maximal voluntary effort , rectal sensory threshold , maximal tolerance volume ( 120 ml ) , and rectoanal inhibitory reflex was present . the colon transit time was delayed ( total 135.6 hours , right colon 66 hours , left colon 56.4 hours , and rectosigmoid colon 13.2 hours ) . based on these findings however , the abdominal distension and constipation were not improved . on the 19th day of hospitalization , a small amount of loose stool was passed and the abdominal pain was relieved . on the 22nd day of hospitalization , the frequency of loose stools increased up to 3 - 4 times / day . oral feeding was started on the 27th day of hospitalization after checking the ct endoscopy ( fig . the finding was marked dilatation of ascending and transverse colon at the level of distal transverse colon without obstructive lesion . the patient was discharged on the 44th day of hospitalization on oral mosapride , itopride , domperidone , and lactitol ( fig . after discharge , she did not have additional symptoms even after the medication was discontinued . she was admitted to a local hospital for 20 days and sigmoidoscopic irrigation and enemas were performed there severe abdominal distension was noted on physical examination and on the simple abdominal radiograph ( fig . 3a ) . the laboratory testing was normal except for alt ( 119 u / l ) and ast ( 141 u / l ) . bisacodyl / docusate was started on hospital day 2 . by hospital day 8 , loose stools were passed after a glycerin enema and the abdominal pain and distension were relieved . on hospital day 10 , a large amount of loose stool was passed and magnesium oxide , mosapride , domperidone , and colonlyte were started . stool passage was increased to 7 - 15 times / day . on hospital day 16 , oral feeding was started and the alt and ast returned to normal . on hospital day 25 , the patient was discharged ( fig . three months later , she visited the outpatient clinic and did not have abdominal distension or constipation without medication ( fig . megacolon can be observed in hirschsprung 's disease , with an infection ( chaga 's disease ) and in some disorders of the endocrine or central nervous system ( including spinal trauma and senility ) . however , in the absence of an organic cause , it is referred to as idiopathic.1,2 idiopathic megacolon is a heterogeneous disorder including idiopathic megarectum , idiopathic megacolon , or a combination of these disorders.3 idiopathic proximal hemimegacolon is defined as megacolon only proximal to the splenic flexure.4 idiopathic proximal hemimegacolon is a very rare and therefore a poorly understood clinical entity . the plausible explanations include abnormalities involving the extrinsic nerves , the enteric nerve plexus , or the intestinal smooth muscle , which could lead to gut dilatation and impaired motility.5 anal manometry is clinically useful in a few patients with chronic constipation , although it has potential value for the exclusion of hirschsprung 's disease , due to the demonstration of internal sphincter relaxation in response to rectal distension.6 the clinical features of patients with idiopathic proximal hemimegacolon are similar to those reported in idiopathic megacolon without megarectum in previous studies . patients with idiopathic megacolon are older than patients with idiopathic megarectum . in this case , the patient experienced her first episode at 44-years of age . most patients present with constipation ; however , documented bowel habits are very variable , from 5 times per day to only once every 3 months . our patient had abdominal distension and pain , normal intelligence , and no familial history . delay in the colon transit is most prominent in the right colon area . in the rectosigmoid area , it is normal.2 - 4,7,8 our patient also showed delay in right colon transit . the abnormal ast / alt levels were considered secondary to hepatocongestion induced by the megacolon . the majority of patients can be successfully managed without surgery.2 for shortening bowel transition time and symptom relief , the prokinetic drugs like mosapride and itopride could be coadministrated.9 however , medical treatment may fail to alleviate symptoms in some patients,8 may be poorly tolerated , and must be continued lifelong to prevent the recurrence of symptoms . megacolon proximal to the splenic flexure is referred to as idiopathic proximal hemimegacolon . here , we present the case of a 44-year - old woman with idiopathic proximal hemimegacolon that had 2 episodes over 4 years .