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Constipation for USMLE

Constipation is defined as infrequent bowel movements or difficulty in bowel movements, and finally constipation may be defined as incomplete defecation. In this handwritten lecture we will be discussing the causes, etiology, diagnosis and treatment of constipation for medical students preparing for the USMLE. ETIOLOGY The main cause of constipation is related to lifestyle factors. Diet of low fiber and fluid, as well as drinking milk, coffee, tea, alcohol. Also lower exercise or immobility. These are the most common cause of constipation. Primary constipation is defined by no underlying cause and no pain. Normal transit constipation is seen when the frequency is normal but difficulty occurs with evacuation. Slow transit constipation occurs when the stool move slowly along the coon. Therefore there is decrease frequency and decrease urgency. Pelvic floor dysfunction can lead to constipation however it requires digital evacuation. Secondary causes of constipation are medications such as opiioids, diuretics, antidepressants, anti-spasmodics, anti-convulsants and Alumimum hydroxide as well as calcium channel blockers. Metabolic causes of constipation include high calcium, Diabetes mellitus, cystic fibrosis, celiacs and hypothyroidism. Muscular causes may be muscular dystrophy. Neurological causes include Parkinson's, Multiple sclerosis, Spinal Cord Injury, Hirschsprung. IBS is primary and pain as well asalternates with diarrhea. Obstruciton due to colon cancer and volvulus. Psychiatric cause are due to fear and pain. DIAGNOSIS History to confirm constipation. Ask about frequency, hardness and difficulty in defecation. Also ask about bloating, distention, abdominal pain, headache, fatigue. Abdominal palpation may show lumps. Rectal exam may show fissure, hemorrhoid, fistulas. Sphincter tone with digital palpation. Feces may show fecal impaction. If there is weight loss bleeding anemia then must rule out colon cancer, especially elderly. X-ray may show stool impaction with gas trapped around it. Colonoscopy is suspecting colon cancer. Barium enema will show the colon as well, but colonoscopy is better. Transit tests include radiopaque marker or radioscintigraphy. Balloon expulsion test to find anal tone. Neurological testing is also importnat. Electromyography and spinal cord injury. Lab work for constipation includes CBC for anemia. Leukocytes for fever and post-op ileus. Thyroid and electrolyts as they are also common causes for constipation. TREATMENT Start with diet and exercise. High fluid and water. Also avoid medications and constipating foods. Pharmacologic therapy for constipation include bulk forming, stool softeners, prokinetics, osmotic, prosecretory. Surgery for constipation is reserved if patients shows symptoms of volvulus, obstruction and ischemia.