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. 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.

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 brown colored or 'coffee ground coloured blood documents presence of UGIB.
• Evidence of bilious material rules out bleeding distal to the pylorus.
• Aspiration of any other GI contents is non-diagnostic.
• After the NGT lavage it's often difficult to determine whether blood in gastric contents is either vomited or from aspiration.
• 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 documented 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.