Bowel Obstruction and NG Tube Care

Medical-Surgical · Gastrointestinal (GI)·Updated 2026-10-28

What it is

A bowel obstruction stops the forward movement of intestinal contents, either mechanically (adhesions, hernias, tumors, volvulus, intussusception) or nonmechanically (paralytic ileus after abdominal surgery, hypokalemia, peritonitis). Fluid, gas and secretions collect above the blockage, so the bowel distends, fluid is lost into the lumen and through vomiting, and rising pressure can cut off the blood supply (strangulation). Care is NPO status, NG decompression, IV fluid and electrolyte replacement, and close watch for strangulation and perforation.

What the NCLEX focuses on

Small bowel obstruction (adhesions most common): rapid onset, colicky pain, early and profuse vomiting, rapid dehydration.
Large bowel obstruction (colorectal cancer most common): gradual onset, marked distention, constipation, lower abdominal cramping, late or absent vomiting.
Bowel sounds are high-pitched above a mechanical obstruction early, then hypoactive or absent; paralytic ileus has absent sounds.
Strangulation or perforation: continuous severe pain, fever, tachycardia, rebound tenderness, rigid abdomen and rising WBC count; this requires emergency surgery.
Vomiting and NG suction remove potassium, sodium, chloride and hydrogen ions, causing hypokalemia, dehydration and metabolic alkalosis.
Salem sump tubes run to low continuous suction with the blue air vent open and above stomach level; single-lumen Levin tubes run to low intermittent suction.
Placement is confirmed by x-ray at insertion, then checked by the external length mark and aspirate pH; auscultating injected air is not reliable.

Priority nursing actions

Keep the client NPO and assess pain, abdominal distention, girth, bowel sounds, emesis and vital signs.
Insert the prescribed NG tube, connect it to suction and keep the head of the bed at 30 degrees or higher.
Start prescribed IV isotonic fluid and potassium replacement; record strict intake and output, including NG drainage.
If drainage stops and nausea or distention increases, check placement and patency first, then irrigate with normal saline as prescribed.
Report signs of strangulation at once and prepare for surgery.
Give mouth and nares care and secure the tube to prevent pressure injury.

Numbers to know

Value	Normal or target	Why it matters
Potassium	3.5 to 5.0 mEq/L (3.5 to 5.0 mmol/L)	Lost through vomiting and suction; hypokalemia worsens ileus
Gastric aspirate pH	5 or less	Supports gastric placement after x-ray confirmation
Head of bed	30 degrees or higher	Reduces aspiration around the tube
Irrigation	30 mL normal saline, as prescribed	Restores patency without injuring the mucosa
Urine output	At least 0.5 mL/kg/h (about 30 mL/h)	Detects dehydration from fluid loss into the bowel

Common exam traps

Choosing oral fluids, a laxative or an enema for suspected mechanical obstruction: wrong because they increase distention and the risk of perforation.
Choosing to increase the suction pressure or clamp the tube when drainage stops: wrong because placement and patency are assessed first.
Choosing to clamp or plug the blue air vent of a Salem sump: wrong because the vent keeps the suction lumen from pulling on the gastric mucosa.
Choosing to reinsert an NG tube that a client pulled out after gastric or esophageal surgery: wrong because blind insertion can disrupt the suture line; notify the surgeon.
Choosing to dismiss new continuous pain and fever as expected: wrong because they signal strangulation.

What to teach

Explain the purpose of NPO status and the NG tube; report nausea, increasing bloating, or the tube feeling loose or displaced.
After discharge, report cramping pain with vomiting, swelling of the abdomen, or no passage of stool or gas.
Prevent constipation with fluids, fiber as tolerated and regular activity.

Try 2 NCLEX-style questions on this topic

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Question 1 · QID 455A4D22

The nurse reviews assessment findings for clients with suspected intestinal obstruction. Classify each finding.

For each finding, identify the most likely clinical concern.

	Early obstruction cue	Possible strangulation/peritonitis	Fluid/electrolyte complication
A: Intermittent cramping with visible abdominal distention
B: Continuous severe pain with rigid abdomen
C: Potassium 3.0 mEq/L after repeated vomiting
D: Fever, tachycardia, and rebound tenderness
E: Orthostatic dizziness and dry mucous membranes

Question 2 · QID 8B144D61

A client with a nasogastric tube for bowel obstruction reports nausea and increasing abdominal distention. The suction canister has had no drainage for 2 hours. Which action should the nurse take first?

Select the best answer.

A. Reposition the client and increase suction pressure before checking tube patency
B. Assess tube placement and patency according to facility procedure
C. Temporarily clamp the tube and reassess abdominal distention after one hour
D. Irrigate the tube immediately with water before assessing its external position

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Sources

Harding MM, Kwong J, Hagler D, Reinisch C. Lewis's Medical-Surgical Nursing: Assessment and Management of Clinical Problems. 12th ed. Elsevier; 2023.
Harding MM, Kwong J, Hagler D, Reinisch C. Lewis's Medical-Surgical Nursing: Assessment and Management of Clinical Problems. 12th ed. Elsevier; 2023; Chapter: Upper Gastrointestinal Problems.
Potter PA, Perry AG, Stockert PA, Hall AM. Fundamentals of Nursing. 10th ed. Elsevier; 2021.

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