What is the best initial imaging study for a patient with black drainage from the Gastrostomy (G)-tube site without issues with tube feeds?

G-Tube Site Black Drainage: Initial Imaging Approach

In a healthcare facility limited to abdominal X-ray or ultrasound, order an abdominal ultrasound to evaluate the G-tube site for complications, as it can assess for peristomal infection, fluid collections, and tube positioning without radiation exposure. 1

Understanding Black Drainage from G-Tube Sites

Black drainage from a G-tube site most commonly represents:

• Hemorrhage with degraded blood products - Bleeding complications occur in 0-2.5% of G-tube placements, with gastric ulceration beneath the internal bolster or traumatic erosion being typical causes 1
• Peristomal infection - The most common G-tube complication, occurring in 5.4-30% of cases, which can produce dark, purulent, or malodorous drainage 1, 2
• Fungal colonization - Can cause tube degradation and dark exudate, reported to cause up to 70% of tube failures by 450 days 1

Why Ultrasound is the Better Choice

Ultrasound provides superior diagnostic information compared to plain X-ray for G-tube site complications:

• Ultrasound can visualize soft tissue changes, fluid collections, peristomal abscesses, and assess tube positioning relative to the gastric wall 3, 4
• Plain abdominal X-rays have extremely limited utility for G-tube site complications - they only confirm tube presence and cannot evaluate soft tissue infection, bleeding, or peristomal pathology 5
• Ultrasound avoids radiation exposure while providing real-time assessment of the site 4

Critical Assessment Points During Ultrasound

The sonographer should specifically evaluate:

• Peristomal soft tissue for fluid collections, abscesses, or cellulitis 2
• Tube position relative to the gastric wall to exclude buried bumper syndrome or migration 1
• Gastric wall integrity to assess for perforation or fistula formation 1
• Presence of free fluid in the peritoneal cavity suggesting peritonitis 1

Immediate Clinical Actions Regardless of Imaging

While awaiting imaging, perform these bedside assessments:

• Inspect the external bolster tension - excessive tightness between internal and external bolsters increases infection risk and can cause pressure necrosis 1, 2
• Look for signs of systemic infection including fever, tachycardia, or peritoneal signs that would indicate urgent surgical consultation 1
• Assess for buried bumper syndrome by checking if the tube is immobile or if there's resistance with formula infusion 1
• Culture the drainage for both bacterial and fungal organisms to guide targeted antimicrobial therapy 2

When Plain X-Ray Might Be Considered

Plain abdominal X-ray has essentially no role in evaluating G-tube site drainage complications but may be ordered only if:

• Concern for bowel obstruction or ileus exists based on clinical symptoms (abdominal distension, inability to tolerate feeds) - though this is not your clinical scenario 1, 5
• Free air under the diaphragm needs to be excluded if peritonitis is suspected, though ultrasound can also detect pneumoperitoneum 1

Critical Pitfalls to Avoid

• Do not assume black drainage is benign - hemorrhage requiring transfusion or laparotomy occurs in fewer than 0.5% of cases but carries significant morbidity 1
• Do not delay imaging if systemic signs develop - peritonitis from perforation occurs in 0.5-1.3% of cases and requires emergency surgical intervention 1
• Do not order plain X-ray expecting it to diagnose the cause of drainage - it has poor diagnostic yield for soft tissue complications and will likely necessitate subsequent ultrasound or CT anyway 5

If Ultrasound Shows Concerning Findings

Based on ultrasound results, escalation may require:

• CT angiography (CTA) of abdomen/pelvis without and with IV contrast if active bleeding is suspected and the patient requires transfer to a higher level of care - this is the gold standard for detecting GI bleeding with 79-85% sensitivity 1, 6
• Surgical or interventional radiology consultation for abscess drainage, tube repositioning, or management of buried bumper syndrome 1, 2
• Endoscopy to directly visualize the gastric mucosa under the internal bolster if hemorrhage or ulceration is confirmed 1