Constipation and Diarrhea

CONSTIPATION

Although frequently a functional problem, constipation may be caused by a variety of treatable organic processes. Any new change in bowel habits should be evaluated for organic causes.

COMMON CAUSES OF CONSTIPATION

Irritable bowel syndrome^*
Diabetes
Diverticulitis
Anorectal disorders (hemorrhoids, anal fissure, fistula or stricture, perianal abscess)^*
Drug ingestion (opiates, anticholinergics, barium sulfate, iron supplements, calcium channel blockers, parasympatholytics, phosphate-containing antacids)

LESS COMMON CAUSES OF CONSTIPATION NOT TO BE MISSED

Hypothyroidism
Hypercalcemia
Rectal carcinoma
Scleroderma
Hypokalemia
Hernia
Sigmoid volvulus
Bowel obstruction

OTHER CAUSES OF CONSTIPATION

Hirschsprung disease
Prolonged inactivity or immobilization
Chagas disease
Myotonic dystrophy

HISTORY

Chronic constipation alternating with episodes of diarrhea suggests irritable bowel syndrome. Anal fissure, perianal abscess, anal fistula, and external hemorrhoids often cause intense pain with defecation, thereby producing constipation through
avoidance. Narrow-caliber stools, with or without blood coating, suggest a rectal fissure, stricture, or rectal carcinoma. Dysphagia, Raynaud phenomenon, and characteristic skin changes suggest scleroderma. Profound constipation is seen in the rare, congenitally acquired aganglionic colon of Hirschsprung disease. Constipation associated with megacolon occurring in patients from Central and South America is often caused by Chagas disease. Vomiting and abdominal pain accompanying constipation are frequently noted in patients with bowel obstruction.

PHYSICAL EXAMINATION

Lower quadrant abdominal pain often accompanied by occult blood in the stool suggests diverticulitis or colorectal carcinoma (although colorectal carcinoma is usually painless early in its course). Anorectal pathology (i.e., anal fissure, external or internal hemorrhoids, perianal abscess) will be noted on examination. Hypothyroidism (obesity, dry skin, coarse hair, and delayed reflexes) may be accompanied by constipation. A mass lesion on digital rectal examination suggests rectal carcinoma. Inguinal hernias and colonic volvulus produce constipation by partial (or complete) bowel obstruction.

DIAGNOSTIC TESTS

Analysis of the stool for gross or occult blood provides information about some of the nonfunctional causes of constipation including diverticulitis and rectal carcinoma. Anoscopy may demonstrate internal hemorrhoids or fissures. The abdominal roentgenogram often demonstrates excessive colonic stool.

SPECIFIC DISORDERS

Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) consists of abnormal intestinal motility, manifest by an increase in slow-wave activity in the colon. Three clinical variants of the disease are recognized: chronic constipation with abdominal pain (IBS-C), chronic intermittent diarrhea without pain (IBS-D) and alternating constipation, and diarrhea usually without pain. Patients with the first two varieties are more commonly seen in the emergency department (ED).

History

IBS affects young or middle-aged adults with a 2:1 female-to-male ratio. Diarrhea occurs intermittently for months or years, with or without intermittent constipation and crampy lower abdominal pain, usually somewhat relieved by passing flatus or stool.

Physical Examination

Physical examination may reveal these a somewhat distended abdomen during episodes of pain. Between episodes of pain, a tender sigmoid filled with feces may be palpated. No definitive tests are available to diagnose IBS; its diagnosis rests entirely on the clinical history and the exclusion of other pathology including celiac disease (gluten intolerance).

Treatment

Treatment includes encouraging the patient to adapt to the symptoms in a way that minimizes impact on lifestyle. Pharmacologic therapy may be helpful in predominant constipation by an increasing dietary bulk. Bloating and cramping
may be relieved with antispasmodic or anticholinergic agents (hyoscyamine or dicyclomine); a mild sedative or a trial of low-dose tricyclic antidepressant therapy may be beneficial. Current specific therapy for IBS-C is lubiprostone (Amitiza), which promotes fluid secretion into the intestinal lumen. IBS-D treatment includes rifaximin (Xifaxan), which inhibits intestinal bacteria, and alosetron (Lotronex), which is a 5-HT₃ receptor antagonist.

Anorectal Disorders

Hemorrhoids are varicosities of the hemorrhoidal venous plexus. External hemorrhoids involve only the inferior venous plexus and lie below the anorectal line. Those cephalad to the dentate line are internal hemorrhoids.
- External hemorrhoids cause pain and bleeding, worsened by defecation. A tender perianal mass is noted on examination.
  - Conservative treatment consists of sitz baths, systemic and local analgesics, stool softeners and avoidance of straining at stool. A topical cream or suppository containing both anesthetic and anti-inflammatory properties, such as Anusol-HC, should be used twice daily.
  - Surgical treatment. Thrombosed hemorrhoids require incision and clot removal. This may be performed in the ED with local anesthesia. With the patient in the lateral decubitus position, the area is prepared and draped and incised to an extent sufficient to allow the removal of the clot. Minor bleeding frequently occurs and may persist for 1 to 3 days. A dry, sterile dressing should be applied and patients should be instructed to start warm sitz baths three to four times daily for 5 to 7 days along with surgical follow-up.
  - Caution is advised to avoid mistaking a nonthrombosed or incompletely thrombosed hemorrhoid for a fully thrombosed hemorrhoid. Nonthrombosed or incompletely thrombosed hemorrhoids are generally pink or erythematous and fluctuant, whereas fully thrombosed hemorrhoids, which may safely be incised and evacuated, are purple or black in color and hard or nonfluctuant; both lesions may be extremely tender. Recognizing these differences is essential because the incision of a partially thrombosed hemorrhoid may precipitate significant hemorrhage.
- Internal hemorrhoids frequently produce a prolapsing anal mass and significant rectal bleeding. Prolapse typically occurs during defecation early in the course of the disease, but eventually permanent prolapse may develop. Anal irritation and intense pruritus often develop in the setting of a mucoid anal discharge. Bleeding is usually intermittent and is rarely massive except in patients with portal hypertension or abnormalities of hemostasis. Hospitalization and surgical excision are recommended when bleeding is significant, when symptoms are severe or disabling, or when conservative treatment has been ineffective.
Anal fissures are linear disruptions of the anal epithelium. The treatment of simple acute fissures is based on maintaining regular, soft bowel movements and the use of sitz baths three to four times per day. Chronic fissures may require surgical excision if conservative measures fail to produce healing and control pain.
Perianal abscess. A perianal abscess is often the acute stage of an anal fistula. When fluctuance is present, incision and drainage is the treatment of choice. When nonfluctuant, warm sitz baths three to four times daily, appropriate antibiotic if systemic evidence of infection is present, and surgical follow-up in 24 to 48 hours are recommended.
Anal fistula. Most anal fistulas are preceded by an anal abscess and arise in an anal crypt. If an anal fistula opens into the rectum above the pectinate line, inflammatory
bowel disease, tuberculosis, lymphogranuloma venereum, rectal cancer, or a foreign body should be considered. Local pruritus, tenderness, and pain worsened by defecation are reported, and recurrent abscesses may develop. Surgical incision or excision under general anesthesia may be required for definitive therapy.
Anorectal stricture. Surgery or trauma to the rectum that denudes the epithelium of the anal canal may result in a rectal stricture. Lymphogranuloma venereum and granuloma inguinale may also lead to stricture formation, as may gonococcal infection. Pain on defecation, constipation, and stools of narrow caliber are the commonest symptoms. Surgical correction may be necessary for patients with severe, chronic stenoses.