PANCE Blueprint GI and Nutrition (9%)

Small bowel obstruction (ReelDx)


61 y/o with acute onset severe abdominal pain and vomiting

Patient will present as → a 65-year-old female with diffuse abdominal pain and vomiting. She has not had a bowel movement in three days. PE reveals high-pitched, hyperactive bowel sounds, tympany to percussion, no rebound tenderness, and a temperature of 100.4 F. Abdominal radiograph reveals distended loops of bowel with a step ladder pattern of differential air-fluid levels.

What is the #1 cause of small bowel obstruction in adults?
Postoperative adhesions
What will the bowel sounds be early on in a small bowel obstruction? What will they be later on?
Early they are hyperactive. Late they are absent.

Small Bowel Obstruction (SBO)

  • Small bowel obstruction presents with abdominal pain, distention, vomiting of partially digested food, and obstipation
  • Bowel sounds are high-pitched and come in rushes. Later in the process, the bowel becomes silent
  • Most small bowel obstructions are due to mechanical obstructions caused by adhesions or hernias; other causes include neoplasm, intussusception, foreign body, inflammatory bowel disease, and volvulus
  • Functional causes of SBO include postoperative ileus (transient paralysis of smooth muscle), infection or inflammation, hypothyroidism, electrolyte abnormalities (hypokalemia and hypercalcemia), and medications (i.e. opioids)
  • Intussusception is the most common cause in children
  • KUB shows dilated loops of bowel with air-fluid levels with little or no gas in the colon.
  • Treat with decompression with an NGT, surgery if a mechanical obstruction is suspected
"Early versus late obstruction: Obstipation and absent bowel sounds are seen late in intestinal obstruction. Hyperactive bowel sounds are very common early in the course of intestinal obstruction. They are described as high-pitched with occasional rushes."

Large Bowel Obstruction

  • The most common location is the sigmoid colon due to neoplasms, fecal impaction, and diverticulitis
  • Presents with distention and pain. Patients may be febrile and tachycardic. Shock may ensue.
  • KUB shows dilated large intestine
  • Barium enema to confirm and establish the location
  • Treatment includes NGT, fluids, pain management, and urgent surgery if a mechanical obstruction is suspected


On the physical exam:

  • In small bowel obstruction, vomiting is more common, and the pain tends to be periumbilical, cramping, and intermittent – with bouts that last for a few minutes at a time
  • In large bowel obstruction, vomiting is less common, and the pain is lower in the abdomen and the bouts of pain are less frequent but last a bit longer

On the abdominal x-ray (KUB):

  • Large bowel obstruction presents with haustra (small pouches caused by sacculation, which give the colon its segmented appearance) that do not transverse bowel
  • Small bowel obstruction presents with valvulae conniventes (white lines passing across the full width of the bowel) that are only found in the small bowel

What finding on abdominal x-ray should make you think of bowel obstruction?
Air fluid levels
For most patients suspected of having mechanical small bowel obstruction, obtain plain radiographs to quickly confirm a diagnosis of bowel obstruction, and, provided the films do not have findings that indicate the need for immediate intervention, then use computed tomography (CT) of the abdomen and pelvis to further characterize the nature, severity, and potential etiologies of the obstruction.” – UpToDate

Upright radiographs may demonstrate the following:

Additional imaging includes an abdominal CT scan with contrast in order to identify the potential cause of obstruction. Abdominal ultrasonography may be useful for individuals with contraindications to CT scanning, like those with contrast allergies and pregnant females.

Small Bowel Obstruction

Treatment includes hospitalization, IV fluids, nothing by mouth, and nasogastric suctioning to remove the fluid and gasses that have built up

  • Urgent surgical consultation is necessary when a mechanical obstruction is suspected

osmosis Osmosis
Intestinal obstruction


An intestinal obstruction occurs when the contents of the gastrointestinal tract cannot pass through the intestines. Signs and symptoms of an obstruction include severe abdominal pain, vomiting, abdominal distension, high-pitched or absent bowel sounds, and increased or absent peristalsis. Fluid and acid-base problems accompany an intestinal obstruction with metabolic alkalosis occurring when an obstruction is high (upper duodenum) due to loss of HCl from vomiting and/or nasogastric suction and dehydration when the obstruction is located in the small intestine. Typically, dehydration and electrolyte imbalance does not usually occur with a large intestine bowel obstruction.

Play Video + Quiz

Question 1
Which of the following is not a radiographic feature of intestinal obstruction?
Multiple air-fluid levels on erect film.
Thumbprinting sign.
The jejunum is characterized by its valvulae conniventes.
Large bowel, except for the caecum, shows haustral folds.
Question 1 Explanation: 
Thumbprinting is a radiographic sign of large bowel thickening caused by edema, related to an infective or inflammatory process.
Question 2
The initial management of intestinal obstruction includes all of the following except
Passage of nasogastric tube for decompression.
See D for explanation 
Placing of intravenous line for rehydration and electrolyte correction.
See D for explanation 
Administering intravenous antibiotics.
See D for explanation 
Question 2 Explanation: 
Treatment is fluid resuscitation, nasogastric suction, and, in most cases of complete obstruction, surgery. If bowel ischemia or infarction is suspected, antibiotics should be given (eg, a 3rd-generation cephalosporin, such as cefotetan 2 g IV) before operative exploration. Surgery, when indicated for acute intestinal obstruction is done after the patient has been adequately resuscitated. All other options are resuscitative measures.
Question 3
Which of the following is associated with the ‘double bubble’ sign on abdominal radiograph?
Duodenal atresia
Pyloric atresia
its radiographic signs are single gas bubble sign, pyloric dimple sign, and absence of a ‘beak’ sign.
Hirschsprung’s disease
In the neonate, this will show dilated loops of bowel with air-fluid levels.
Sigmoid volvulus
Abdominal radiograph shows Frimann Dahl’s sign.
Question 3 Explanation: 
Abdominal plain films in neonates with duodenal atresia will demonstrate dilated stomach and duodenum giving the characteristic ‘double bubble’ sign with no gas distal to the duodenum.
Question 4
Which of the following is not a cause of paralytic ileus
Gastrointestinal surgery
See D for explanation
See D for explanation
Intra-abdominal sepsis
See D for explanation
Question 4 Explanation: 
Hyperkalemia does not cause paralytic ileus. It can cause cardiac arrhythmia. All other options are correct.
Question 5
Which of the following is correct concerning large bowel obstruction
Vomiting occurs early and is profuse with rapid dehydration
Seen in high small bowel obstruction.
Pain is predominant with central distension.
Seen in high small bowel obstruction.
Distension is minimal.
Distension is minimal in small bowel obstruction.
Vomiting and dehydration are late.
Question 5 Explanation: 
In large bowel obstruction, distension is early and pronounced. Pain is mild and vomiting and dehydration are late.
There are 5 questions to complete.
Shaded items are complete.

References: Merck Manual · UpToDate

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