Lower gastrointestinal bleeding other diagnostic studies

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] ; Associate Editor(s)-in-Chief: Aditya Ganti M.B.B.S. [2]

Overview

Nasogastric tube lavage may be helpful in the diagnosis of lower gastrointestinal bleeding. NGT helps in differentiating LGIB from UGIB.

Other Imaging Findings

Nasogastric lavage

• Nasogastric lavage is only indicated when the diagnosis of UGIB doubtful.
• It is rarely used.
• Nasogastric lavage also helps in documenting active or recent UGIB and the need for urgent endoscopy.
• Occasionally used to empty gastric contents in preparation for endoscopy.

Interpretation

• Evidence of old (brown colored or 'coffee grounds') or fresh blood documents presence of UGIB.
• Evidence of bilious material rules out bleeding distal to the pylorus.
• Any other appearances of GI contents are non-diagnostic.
• There is no evidence that performing a nasogastric lavage to clear clots or otherwise manage bleeding improves clinical outcome.
• Determining whether blood is in gastric contents, either vomited or aspirated specimens, is surprisingly difficult.
• Slide tests are based on orthotolidine (Hematest reagent tablets and Bili-Labstix) or guaiac (Hemoccult and Gastroccult).
• Rosenthal found orthotolidine-based tests more sensitive than specific; the Hemoccult test's sensitivity reduced by the acidic environment; and the Gastroccult test be the most accurate. Cuellar found the following results:

Determining whether blood is in the gastric aspirate

Finding	Sensitivity	Specificity	Positive predictive value (prevalence of 39%)	Negative predictive value (prevalence of 39%)
Gastroccult	95%	82%	77%	96%
Physician assessment	79%	55%	53%	20%

• Holman used simulated gastric specimens and found the Hemoccult test to have significant problems with non-specificy and false-positive results, whereas the Gastroccult test was very accurate.

Contraindications

• Avoid gastric lavage in patients with suspected perforated abdominal viscus.

Complicatiions

Complications of the procedure include:

• Bleeding from trauma during tube passage in patients with coagulopathy is a possible complication.
• Other rare complications include
  • Pharyngeal and esophageal perforation
  • Cardiac arrest
  • Ethmoid sinus fracture with brain trauma
  • Bronchial intubation.