Bowel sounds, absent [Silent abdomen]

Absent bowel sounds refers to an inability to hear any bowel sounds with a stethoscope in any quadrant after listening for at least 5 minutes. Bowel sounds cease when mechanical or vascular obstruction or neurogenic inhibition halts peristalsis. When peristalsis stops, gas from bowel contents and fluid secreted from the intestinal walls accumulate and distend the lumen, leading to life-threatening complications (such as perforation, peritonitis, and sepsis) or hypovolemic shock.

Simple mechanical obstruction, resulting from adhesions, hernia, or tumor, causes loss of fluids and electrolytes and induces dehydration. Vascular obstruction cuts off circulation to the intestinal walls, leading to ischemia, necrosis, and shock. Neurogenic inhibition, affecting innervation of the intestinal wall, may result from infection, bowel distention, or trauma. It may also follow mechanical or vascular obstruction or metabolic derangement such as hypokalemia.

Abrupt cessation of bowel sounds, when accompanied by abdominal pain, rigidity, and distention, signals a life-threatening crisis requiring immediate intervention. Absent bowel sounds following a period of hyperactive sounds are equally ominous and may indicate strangulation of a mechanically obstructed bowel.

Emergency interventions

If you fail to detect bowel sounds and the patient reports sudden, severe abdominal pain and cramping or exhibits severe abdominal distention, prepare to insert a nasogastric (NG) or intestinal tube to suction lumen contents and decompress the bowel. (See Are bowel sounds really absent?) Administer I.V. fluids and electrolytes to offset dehydration and imbalances caused by the dysfunctioning bowel.

Because the patient may require surgery to relieve an obstruction, withhold oral intake. Take the patient's vital signs, and be alert for signs of shock, such as hypotension, tachycardia, and cool, clammy skin. Measure abdominal girth as a baseline for gauging subsequent changes.

History and physical examination

If the patient's condition permits, proceed with a brief history. Start with abdominal pain: When did it begin? Has it gotten worse? Where does he feel it? Ask about a sensation of bloating and about flatulence. Find out if the patient has had diarrhea or has passed pencil-thin stools — possible signs of a developing luminal obstruction. The patient may have had no bowel movements at all — a possible sign of complete obstruction or paralytic ileus.

Ask about conditions that commonly lead to mechanical obstruction, such as abdominal tumors, hernias, and adhesions from past surgery. Determine if the patient was involved in an accident — even a seemingly minor one, such as falling off a stepladder — that may have caused vascular clots. Check for a history of acute pancreatitis, diverticulitis, or gynecologic infection, which may have led to intra-abdominal infection and bowel dysfunction. Be sure to ask about previous toxic conditions, such as uremia, and about spinal cord injury, which can lead to paralytic ileus.

If the patient's pain isn't severe or accompanied by other life-threatening signs or symptoms, obtain a detailed medical and surgical history and perform a complete physical examination followed by an abdominal assessment and pelvic examination.

Start your assessment by inspecting the abdominal contour. Stoop at the recumbent patient's side and then at the foot of his bed to detect localized or generalized distention. Percuss and palpate the abdomen gently. Listen for dullness over fluid-filled areas and tympany over pockets of gas. Palpate for abdominal rigidity and guarding, which suggest peritoneal irritation that can lead to paralytic ileus.

Medical causes

❑ Complete mechanical intestinal obstruction. Absent bowel sounds follow a period of hyperactive bowel sounds in this potentially life-threatening disorder. This silence accompanies acute, colicky abdominal pain that arises in the quadrant of obstruction and may radiate to the flank or lumbar regions. Associated signs and symptoms include abdominal distention, and bloating, constipation, and nausea and vomiting (the higher the blockage, the earlier and more severe the vomiting). In late stages, signs of shock may occur with fever, rebound tenderness, and abdominal rigidity.

❑ Mesenteric artery occlusion. With mesenteric artery occlusion, a life-threatening disorder, bowel sounds disappear after a brief period of hyperactive sounds. Sudden, severe midepigastric or periumbilical pain occurs next, followed by abdominal distention, bruits, vomiting, constipation, and signs of shock. Fever is common. Abdominal rigidity may appear later.

❑ Paralytic (adynamic) ileus. The cardinal sign is absent bowel sounds. In addition to abdominal distention, associated signs and symptoms of paralytic ileus include generalized discomfort and constipation or the passage of small, liquid stools. If paralytic ileus follows acute abdominal infection, the patient may also experience fever and abdominal pain.

Other causes

❑ Abdominal surgery. Bowel sounds are normally absent after abdominal surgery — the result of anesthetic use and surgical manipulation.

Special considerations

After you've inserted an NG or intestinal tube, elevate the head of the patient's bed at least 30 degrees, and turn the patient to facilitate passage of the tube through the GI tract. (Remember not to tape an intestinal tube to the patient's face.) Ensure tube patency by checking for drainage and properly functioning suction devices, and irrigate accordingly.

Continue to administer I.V. fluids and electrolytes, and make sure that you send a serum specimen to the laboratory for electrolyte analysis at least once per day. The patient may need X-ray studies and further blood work to determine the cause of absent bowel sounds.

After mechanical obstruction and intra-abdominal sepsis have been ruled out as the cause of absent bowel sounds, give the patient drugs to control pain and stimulate peristalsis. Remember that opioids may slow peristalsis.

Pediatric pointers

Absent bowel sounds in children may result from Hirschsprung's disease or intussusception, both of which can lead to life-threatening obstruction.

Geriatric pointers

Older patients with a bowel obstruction that doesn't respond to decompression should be considered for early surgical intervention to avoid the risk of bowel infarct.

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Book Source Details

• Book Title: Handbook of Signs & Symptoms (Third Edition)
• Author(s): Springhouse
• Year of Publication: 2006
• Copyright Details: Handbook of Signs & Symptoms (Third Edition), Copyright © 2006 Lippincott Williams & Wilkins.

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Copyright Details: Handbook of Signs & Symptoms (Third Edition), Copyright © 2008 Williams & Wilkins.

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