Irritable bowel syndrome is a clinical diagnosis

Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.

A 25-year-old woman is evaluated for a 2-year history of almost daily bloating and lower abdominal cramping; the symptoms are associated with constipation, relieved with bowel movements, and seem worse when she is under stress. She has one or two small bowel movements a week and often has a feeling of incomplete evacuation. She never has diarrhea and has not had blood in the stool, nocturnal awakening with pain or for bowel movements, or weight loss. She has taken a fiber supplement without relief. The patient is otherwise healthy, and her only medication is an oral contraceptive pill that she has been taking for 1 year. Her mother had a similar condition when she was younger, but both her parents are alive and well.

On physical examination, vital signs are normal; there is mild lower abdominal tenderness with no rebound, guarding, or palpable abdominal masses. Laboratory studies reveal a hemoglobin level of 13.1 g/dL (131 g/L); results of serum biochemistry tests, including thyroid-stimulating hormone, are normal.

Which of the following is the most appropriate next step in the management of this patient?

A) Colonoscopy
B) CT scan of the abdomen and pelvis
C) Discontinue the oral contraceptive
D) Reassurance and polyethylene glycol

MKSAP Answer and Critique

The correct answer is D) Reassurance and polyethylene glycol. This item is available to MKSAP 15 subscribers as item 38 in the Endocrinology and Metabolism section. MKSAP 16 will release Part A on July 31. More information is available online.

This patient has irritable bowel syndrome. As a young woman, she fits the demographic profile, and she also meets the Rome III criteria, with abdominal pain relieved by defecation and a change in bowel habits. The most recent formal criteria are the Rome II criteria, which require the presence of at least two of three symptoms occurring for 3 months (not necessarily consecutive) during a 12-month period. These symptoms include pain relieved with defecation, onset associated with change in stool frequency, or onset associated with change in the consistency of the stool. In clinical practice, these criteria have a positive predictive value of 98%. Importantly, she has no alarm indicators, including older age, male sex, nocturnal awakening, rectal bleeding, weight loss, or family history of colon cancer. In the absence of alarm symptoms, additional tests have a diagnostic yield of 2% or less. Furthermore, laboratory studies indicate no anemia or thyroid deficiency.

Irritable bowel syndrome is a clinical diagnosis, and there are no laboratory, radiographic, or endoscopic findings that aid in diagnosis. Additional evaluation is not only unnecessary and expensive but also potentially harmful, especially when invasive procedures are ordered; additionally, confidence in the diagnosis is undermined when serial testing is ordered. The patient should be reassured that although this problem is annoying and inconvenient, it is not life-threatening. The patient has constipation-predominant irritable bowel syndrome, and her symptoms will likely be alleviated if she has more frequent and satisfying bowel movements. Because fiber supplementation has not been helpful, a nonabsorbed osmotic laxative such as polyethylene glycol will likely provide her significant relief.

There is no indication for the patient to undergo a CT scan or colonoscopy. Oral contraceptives are not typically associated with the syndrome, and she began taking the medication after the onset of her symptoms.

Key Point

Irritable bowel syndrome is a clinical diagnosis that can be made confidently when patients meet the Rome III criteria and do not have alarm indicators.

Learn more about ACP’s MKSAP 16.

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