What is the best course of action for a 56-year-old male presenting with bloating, abdominal fullness, no abdominal tenderness, tachycardia, and frequent loose bowel movements?

Immediate Evaluation and Management

This patient requires urgent evaluation for bowel obstruction or ischemia given the combination of tachycardia (HR 124), bloating, abdominal fullness, and frequent loose bowel movements, despite the absence of tenderness.

Critical Initial Assessment

The tachycardia is the most concerning feature and demands immediate investigation for serious pathology 1, 2. Tachycardia in the setting of abdominal symptoms is a warning sign of bowel ischemia, strangulation, or impending perforation 1, 2.

Immediate Diagnostic Workup Required

• CT abdomen/pelvis with IV contrast is mandatory - this is the diagnostic standard with >90% accuracy and can identify bowel obstruction, ischemia (abnormal bowel wall enhancement, mesenteric edema, pneumatosis), or perforation 1, 2
• Complete blood count to assess for leukocytosis (suggests ischemia or infection) 2
• Serum lactate level - elevated lactate indicates bowel ischemia and mandates emergency surgery 1, 2
• Electrolyte panel and renal function to assess dehydration from diarrhea 2
• Stool studies for Clostridium difficile, ova and parasites, and viral pathogens to exclude infectious causes 3

Physical Examination Red Flags to Assess

• Fever, tachypnea, confusion - these combined with tachycardia indicate strangulation/ischemia 2
• Peritoneal signs (guarding, rebound tenderness, rigidity) - their absence does NOT exclude serious pathology, especially in elderly patients where pain may be less prominent 2
• Bowel sounds - absent sounds suggest ischemia or strangulation with mortality up to 25% if not immediately treated; hyperactive sounds with rushes suggest mechanical obstruction 2
• Abdominal distension - present in 65% of bowel obstruction cases 2
• Digital rectal exam - assess for blood (suggests colorectal cancer or ischemia) or rectal mass 2

Initial Stabilization While Awaiting Imaging

• IV crystalloid resuscitation to correct dehydration from diarrhea 1
• Nasogastric tube decompression if vomiting develops or obstruction is suspected 1
• Foley catheter to monitor urine output and assess volume status 1
• Broad-spectrum antibiotics if perforation or ischemia is suspected based on clinical presentation 1
• NPO status until obstruction is excluded 1

Decision Algorithm Based on CT Findings

If CT Shows Bowel Obstruction with Ischemia Signs

Immediate emergency surgery is required if any of the following are present 1:

• Pneumatosis intestinalis
• Free intraperitoneal air
• Bowel wall thickening with poor enhancement
• Closed-loop obstruction
• Peritoneal signs on exam
• Lactic acidosis

If CT Shows Simple Obstruction Without Ischemia

• Continue NPO, IV fluids, nasogastric decompression 1
• Serial abdominal exams every 4-6 hours 1
• Repeat lactate levels 1
• Surgery consultation for observation and potential intervention 1

If CT is Normal - Consider Functional Causes

Only after excluding obstruction and ischemia should functional causes be considered 3.

Diagnostic Evaluation for Functional Disorders

For patients over age 50 with new-onset symptoms, colonoscopy is mandatory to exclude colon cancer, even without alarm features, due to higher pretest probability 3.

Screen for infectious and inflammatory causes 3:

• Stool for ova and parasites (especially if travel history or endemic area)
• Fecal calprotectin to exclude inflammatory bowel disease
• Celiac serology (tissue transglutaminase IgA with total IgA) if chronic symptoms 4

Additional testing based on symptom pattern 3:

• Lactose/dextrose H2 breath test for carbohydrate malabsorption
• Small bowel biopsies for giardia or malabsorption if watery diarrhea persists
• Colonic biopsies for microscopic colitis

Treatment for Functional Diarrhea-Predominant Symptoms

If all structural and infectious causes are excluded 3:

First-line antidiarrheal therapy 3, 5:

• Loperamide 4 mg PO initially, then 2 mg after each loose stool, maximum 16 mg/day 3, 5
• Clinical improvement usually observed within 48 hours 5
• If no improvement in 48 hours, discontinue and reassess 5

Monitor for warning signs requiring immediate discontinuation 5:

• Fever or abdominal distention developing during treatment
• Blood in stools
• Fainting, rapid or irregular heartbeat, or unresponsiveness (cardiac toxicity)

Alternative agents if loperamide ineffective 3:

• Diphenoxylate/atropine 1-2 tablets PO every 6 hours PRN (maximum 8 tablets/day) if patient not on opioids 3

For bloating symptoms specifically 3:

• Antispasmodic agents (anticholinergics) particularly if symptoms worsen with meals 3
• Tricyclic antidepressants if pain is frequent and disabling 3

Critical Pitfalls to Avoid

• Never attribute tachycardia to anxiety alone - it may be the only early sign of bowel ischemia before peritoneal signs develop 1, 2
• Do not start antidiarrheal agents before excluding obstruction - this can worsen obstruction and precipitate toxic megacolon 3
• Do not delay CT imaging based on absence of abdominal tenderness - elderly patients and those with early ischemia may have minimal tenderness 2
• Do not mistake overflow diarrhea around an impaction for gastroenteritis - this is a common error that delays diagnosis of obstruction 2
• Do not use plain abdominal X-rays as the primary diagnostic tool - they have only 50-60% sensitivity and are non-diagnostic in 36% of cases 2