enteric fistulae are a complex and technically frustrating complication of any bowel surgery with high morbidity and mortality , associated prolonged hospital stay and greater healthcare costs . they are most often seen in the post - operative period secondary to an anastomotic leak and typically follow surgery for cancer or inflammatory bowel disease . this particular case highlights the constellation of symptoms that can arise with entero - enteric fistulae , which , given a background of previous bowel cancer , can mimic disease recurrence . a 71-year - old male presented with a 10-month history of chronic diarrhoea , weight loss and left lower quadrant pain . he complained of increased frequency of bowel motions with up to 10 motions a day , abdominal pain and a weight loss of > 10 kg . three years previously he had undergone an extended right hemi - colectomy and adjuvant chemotherapy for a pt3 n1 m0 moderately differentiated adenocarcinoma in the transverse colon . his surgical history included diverticular disease with a previous diverticular perforation managed conservatively , bilateral total hip replacements and bilateral inguinal hernia repairs . in addition , he was a cigarette smoker of 80 pack - years . clinical examination revealed no abdominal tenderness and no masses palpated per rectum . on further investigation , however , his serum carcinoembryonic antigen ( cea ) level was noted to be elevated with a peak post - operative cea of 14.8 g / dl when he presented 48 months after his initial surgical resection . subsequent computed tomography ( ct ) of the thorax , abdomen and pelvis was negative for disease recurrence ; however , an 18-fluorodeoxyglucose ( 18-fdg ) positron emission tomography contrast - enhanced ct ( pet / cect ) scan showed diffuse low - grade 18-fdg uptake within the mesenteric fat as well as near the site of the previous anastomosis , suspicious for peritoneal metastatic disease ( fig .  1 ) . repeat colonoscopy did not identify any luminal abnormality , and the decision was made to perform an elective diagnostic laparoscopy . figure  1:axial pet ct showing increased fdg uptake in the mesentery of the left upper quadrant suspicious for metastatic recurrence . axial pet ct showing increased fdg uptake in the mesentery of the left upper quadrant suspicious for metastatic recurrence . intra - operatively , there were dense adhesions to the anterior abdominal wall , and it was decided to proceed to laparotomy . the adhesions were divided , and a fistula was subsequently identified between the redundant stump of the ileal - colic end - to - side anastomosis and the jejunum ( figs  2 and 3 ) . the jejunal segment involving the fistula was resected and a jejuno - jejunal hand - sewn end - to - end anastomosis performed . two large mesenteric lymph nodes were excised , and biopsies were also taken from dense adhesions . all resected tissues were sent to histopathology ; these were all subsequently reported as clear of malignant disease . the patient was subsequently discharged day 12 post - operatively after an uneventful clinical course . figure  3:jejunal - ileal fistula originating from the stump of the previous end - to - side ileocolic anastomosis . jejunal - ileal fistula originating from the stump of the previous end - to - side ileocolic anastomosis . the majority of intestinal fistulae are due to preceding surgery ; complications from abdominal surgery are the main cause of 80% of small bowel fistulae . these fistulae may occur from anastomotic suture line breakdown , inadvertent iatrogenic enterotomy or small bowel injury at the time of closure . inadequate blood flow from devascularization or tension at the anastomotic suture lines , anastomosis of diseased bowel or perianastomotic abscess may compromise the integrity of surgical anastomoses . thus , when performing any bowel anastomosis , one must pay careful attention to the basic principles of ensuring a tension - free repair and good blood supply to the bowel segments . clinical presentation of enteric fistulae varies depending on what portions of the bowel are affected and length of bowel bypassed by the fistula . typically , diarrhoea and weight loss are the cardinal symptoms of entero - enteric fistulae ; however , patients can also be asymptomatic when only a small segment of bowel is bypassed . this patient presented with chronic diarrhoea , weight loss and abdominal cramping in keeping with an entero - enteric fistula bypassing a significant portion of bowel . his previous history of bowel cancer coupled with continuously rising cea levels , however , was suggestive of a possible cancer recurrence . cea monitoring post - surgical resection aims to identify cancer recurrence at an early and treatable stage . we know that rising post - operative cea levels indicate high probability of cancer recurrence . however , there is considerable variation in sensitivity and specificity rates in the literature , and a variety of other conditions have been shown to increase serum levels of cea such as smoking and benign liver disease [ 6 , 7 ] . although this patient 's follow - up endoscopy and ct imaging revealed no indication of disease recurrence , the pet ct showed areas of fdg uptake very suspicious for disease recurrence ( fig .  1 ) . in a recent study of 69 patients by ozkan et al . , the sensitivity and specificity of 18f - fdg pet / ct in the detection of disease recurrence were calculated as 97 and 61% , respectively . there was no correlation between patients ' serum cea levels and lesions ' maximum standardized uptake values . gauthe et al . reported pet / cect 's sensitivity and specificity in detection of tumour recurrence in colorectal cancer ( crc ) patients with elevated cea as 94.1 and 77.2% , respectively . this patient 's peak post - operative cea was 14.8 g / dl when he presented 48 months after his initial surgical resection with his symptoms . as such , the decision to proceed with exploratory surgery was made because of the unfavourable results of the biochemical and radiological investigations . routine pet / cect as a means of crc surveillance is not indicated and is actively discouraged . however , given the patient 's elevated serum cea and negative ct imaging and endoscopy , its use is recommended . despite the underlying aetiology , this case illustrates that imaging with pet / cect can be a powerful modality in ultimately affecting patient management . intestinal fistula should always be considered in a patient with a previous history of bowel surgery presenting with diarrhoea and weight loss . this particular case highlights the constellation of symptoms that can arise with entero - enteric fistulae , which , given a background of previous bowel cancer with adjuvant chemo radiotherapy , can mimic disease recurrence . imaging and the use of tumour markers following surgery can be misleading , and definitive diagnosis with laparoscopy or laparotomy is essential to establish recurrence of disease where doubt exists . ethical approval : written informed consent was obtained from the patient in question for both images used and permission to publish  a copy of consent is available on request . author contributions : n.e . involved in writing of manuscript , acquisition of data , and manuscript editing . c.c . participated in manuscript editing .
enteric fistulae are a complex and technically frustrating complication of any bowel surgery . 
 the constellation of associated non - specific symptoms often leads to extensive investigation and , in this case , suspicion of disease recurrence . a 71-year - old gentleman with a history of previous colorectal cancer presented with chronic diarrhoea , weight loss and left lower quadrant pain . 
 elective exploratory laparoscopy was performed to investigate possible disease recurrence due to elevated carcinoembryonic antigen levels and a positron emission tomography positive area within the mesentery . 
 a jejunal  ileal fistula was found at laparotomy where the blind ileal stump of the end - to - side ileocolic anastomosis had fistulated into the jejunum . 
 resection of the affected jejunum was performed with end - to - end jejuno - jejunal re - anastomosis and stapling of the ileal stump . 
 specimen histology was negative for recurrence . 
 intestinal fistulae represent a diagnostic challenge . 
 this is the first case report describing an enteric fistula mimicking cancer recurrence .