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Chronic diarrhoea in an elderly woman

BMJ 2011; 342 doi: https://doi.org/10.1136/bmj.c7339 (Published 31 March 2011) Cite this as: BMJ 2011;342:c7339
  1. Jacqueline K Simpson, foundation year 1 trainee,
  2. Anna L Timmis, foundation year 2 trainee,
  3. Shahab Siddiqi, consultant colorectal surgeon
  1. 1Chase Farm Hospital, London EN2 8JL, UK
  1. Correspondence to: J K Simpson jacquelinesimpson{at}doctors.org.uk

An 89 year old woman was admitted with a six week history of severe watery brown diarrhoea. She had not travelled recently or changed her diet, but she had lost half a stone (3 kg) in weight. She had a history of diverticulosis, recurrent urinary tract infections, and hypertension but no family history of cancer. She was a non-smoker who lived alone and was independently mobile with a frame, requiring no package of care.

On examination she was afebrile, her pulse was 95 beats/min, and her blood pressure was 150/88 mm Hg. Her abdomen was soft and non-tender. Per rectal examination and a plain abdominal film were unremarkable. Bloods on admission showed raised inflammatory markers, and within days of admission her electrolytes became deranged, with hypernatraemia (sodium 158 mmol/L) and hypokalaemia (potassium 2.5 mmol/L). Blood gas results showed a metabolic alkalosis (pH 7.52, pCO2 37 mm Hg, bicarbonate 31 mmol/L) and hyperchloraemia (chloride 116 mmol/L). Cloudy urine, which was positive for Escherichia coli, was collected after insertion of a urinary catheter. Stool culture and Clostridium difficile toxin were negative. Flexible sigmoidoscopy showed sigmoid diverticulosis, and a random biopsy showed a mild increase in chronic inflammatory cells.

Figures 1 and 2 show axial and sagittal computed tomograms of the abdomen


Fig 1 Axial computed tomogram of the abdomen


Fig 2 Sagittal computed tomogram of the abdomen


  • 1 What abnormality is seen on the computed tomogram of the abdomen?

  • 2 What are the differential diagnoses and the most likely diagnosis in this case?

  • 3 Can you explain the electrolyte derangement?

  • 4 What other investigations might help make the diagnosis?

  • 5 How should she be treated?


1 What abnormality is seen on the computed tomogram of the abdomen?

Short answer

Air-fluid level in the bladder (fig 3).


Fig 3 Axial computed tomogram showing air in the bladder (arrow)

Long answer

The axial computerised tomogram of the abdomen shows an air-fluid level in the bladder, inflammatory changes around the adjacent rectum, and an extraluminal locule of air in the left anterolateral aspect of the rectum, which probably represents the fistula (fig 4).


Fig 4 Sagittal computerised tomogram showing an air-fluid level in the bladder and a locule of air posterior to the bladder, probably representing the fistula (arrow). There is also a uterine fibroid, marked by a thin arrow

2 What are the differential diagnoses and the most likely diagnosis in this case?

Short answer

The differential diagnoses for air in the bladder are colovesical fistula, emphysematous cystitis, or gas introduced by instrumentation.1 In view of the history and clinical findings, a colovesical fistula secondary to diverticular disease is the most likely diagnosis.

Long answer

Colovesical fistula is the most likely one of the differential diagnoses to present with such severe electrolyte derangement. Our patient had a history of diverticular disease, which was confirmed on flexible sigmoidoscopy, making diverticular disease the probable underlying condition.

Colovesical fistulas are seen in patients with diverticular disease; colonic carcinoma; Crohn’s colitis; and previous gastrointestinal surgery, radiotherapy, appendicitis, carcinoma of the bladder, and trauma.2 Two retrospective studies found that 70-75% of cases were caused by sigmoid diverticulitis.2 3

A colovesical fistula is an abnormal connection between the colon and the urinary bladder that allows the diversion of faecal material into the bladder. Fistula formation occurs in an area of intense inflammation, often related to a pericolic diverticular abscess. The abscess may adhere to the bladder and then rupture into the bladder, resulting in a persistent fistula.2 4

Colovesical fistula may present with pneumaturia or faecaluria, which are pathognomonic,5 or more insidiously with dysuria and recurrent urinary tract infection.6 Diarrhoea is a more rare presenting symptom and may be a result of diverticular colitis. Diverticular colitis has been shown histologically to have similarities with inflammatory bowel disease and be a cause of chronic diarrhoea.7 8

3 Can you explain the electrolyte derangement?

Short answer:

The electrolyte derangement resulted from the diarrhoea causing hypokalaemia, which was potentiated by hypovolaemia and the activation of the renin-angiotensin-aldosterone pathway.

Long answer

The electrolyte derangement is not completely attributable to urine being in contact with bowel mucosa, because this tends to cause hyperchloraemic metabolic acidosis and our patient had alkalaemia.9 The patient’s diarrhoea caused gastrointestinal water loss, which probably also resulted in loss of potassium ions and secondary hypernatraemia.10 11 12 In hypokalaemia intracellular potassium ions are exchanged for extracellular hydrogen ions and this might explain the alkalosis.12 13 The diarrhoeal water loss will have caused hypovolaemia and activated the renin-angiotensin-aldosterone pathway, thereby increasing renal sodium, water, and chloride resorption in exchange for potassium excretion. This would worsen the hypernatraemia, hyperchloraemia, hypokalaemia, and the subsequent alkalosis.12 13

4 What other investigations might help make the diagnosis?

Short answer

Other investigations include magnetic resonance imaging, cystoscopy, cystography, and water soluble enema.

Long answer

Computed tomography is the first line investigation for complicated diverticular disease. The key here is to make a diagnosis, assess the cause of the fistula, detail the anatomy of the fistula, and then plan treatment, which may involve surgery. In retrospective case series, computed tomography had higher rates of fistula detection than ultrasonography, barium studies, colonoscopy, cystoscopy, cystography, and excretory urography.14 15 In addition, computed tomography enables extraluminal and intraluminal processes to be seen and staging to be carried out if malignancy is a possibility. Colonoscopy and cystoscopy may be useful in addition to computed tomography to exclude malignancy or obtain a histological diagnosis.5 14 Fistulograms are not used in colovesical fistula because there is no cutaneous connection.

Magnetic resonance imaging is the reference standard for fistula detection and study of the anatomy of the tract in perianal and small bowel Crohn’s disease.16 17 It also has a high sensitivity and specificity in the detection of colovesical fistulas and elucidation of their aetiology,18 and is an alternative to computed tomography.

5 How should she be treated?

Short answer

Treatment options include antibiotics, control of sepsis, correction of electrolyte disturbance, drainage of any collections, and surgery.

Long answer

Conservative management consists of correction of electrolyte derangement and treatment of and then prophylaxis for recurrent urinary sepsis, which is the main cause of morbidity.19 Percutaneous drainage of collections may enable surgery to be avoided, improve sepsis, and allow fistulous connections to heal.20 A recent case report found that administration of the somatostatin analogue octreotide in malignant colovesical fistula resulted in closure of the fistula and improvement in pain.21 However spontaneous closure is rare, occurring in only 2% of patients, so surgery is recommended in those who are fit.22

Surgical options in our patient included sigmoid colectomy with primary anastomosis, simple colostomy to divert the faecal stream, and Hartmann’s procedure (exteriorising the proximal colon to form an end colostomy with closure of the distal rectal stump). Surgery involving larger resections and the bladder is rarer and mostly confined to malignant cases.3 5 Surgical management has a variable prognosis, with two recent case note studies showing less than 2% operative mortality.3 5 However, a recent review of postoperative outcomes after colovesical fistula found complication rates of 4-49%.22

Patient outcome

Our patient had conservative treatment before the diagnosis was confirmed, but these measures alone failed to correct the electrolyte derangement and she continued to deteriorate. She opted for surgery and underwent a defunctioning loop colostomy because resectional surgery was deemed too high risk. The initial outcome was excellent, with resolution of sepsis and electrolyte imbalance. However, three weeks after she became depressed, started refusing rehabilitation, and eventually stopped eating and drinking. A week after this she was placed on an end of life care pathway and died shortly afterwards. No further episodes of sepsis or electrolyte imbalance occurred postoperatively until near death.


Cite this as: BMJ 2011;342:c7339


  • Competing interests: All authors have completed the Unified Competing Interest form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

  • Provenance and peer review: Not commissioned; externally peer reviewed.

  • Patient consent obtained when she had full capacity.


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