What is the likely diagnosis and recommended work‑up and management for a patient with abdominal pain, diarrhea, abdominal tenderness, back pain, dry skin, pruritus, and a squeezing sensation on urination?

Differential Diagnosis and Management Approach

Most Likely Diagnosis: Infectious Diarrhea with Possible Urinary Tract Involvement

The constellation of abdominal pain, diarrhea, abdominal tenderness, and urinary symptoms (squeezing sensation when urinating) most strongly suggests infectious diarrhea with possible concurrent urinary tract infection or dehydration-related urinary symptoms. The back pain and dry skin with itching likely represent dehydration sequelae rather than primary pathology. 1

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Immediate Clinical Assessment

Vital Signs and Volume Status

• Check for fever, tachycardia, orthostatic blood pressure changes, and signs of dehydration (dry mucous membranes, decreased skin turgor, absent jugular venous pulsations) immediately. 1
• Assess for signs of severe dehydration: thirst, decreased urination, lethargy, and altered sensorium. 1
• The "squeezing sensation" during urination combined with dry skin suggests significant volume depletion affecting renal perfusion. 1

Physical Examination Priorities

• Palpate for localized versus generalized abdominal tenderness and check for peritoneal signs (guarding, rebound tenderness) to exclude perforation or peritonitis. 1
• Perform digital rectal examination to assess stool characteristics (bloody, mucous, purulent) and exclude fecal impaction with overflow diarrhea. 1, 2
• Examine for abdominal distension and listen for bowel sounds (hyperactive suggests enteritis; absent suggests ileus or obstruction). 1

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Critical History Elements

Diarrhea Characterization

• Document onset timing (abrupt versus gradual), stool frequency, volume, and characteristics (watery, bloody, mucous, greasy). 1
• Ask specifically about fever, tenesmus, blood or pus in stool—these inflammatory features suggest shigellosis, salmonellosis, or campylobacteriosis. 1
• Duration >1 day with fever, bloody stools, or dehydration mandates fecal specimen evaluation. 1

Epidemiologic Risk Factors

• Recent travel to developing areas, daycare exposure, consumption of raw meats/eggs/shellfish, untreated water, or contact with sick individuals. 1
• Recent antibiotic use (raises concern for Clostridioides difficile), immunosuppression (HIV, steroids), or extremes of age. 1, 3

Urinary Symptoms

• The "squeezing sensation" may represent dysuria from urinary tract infection, urethral irritation from dehydration, or referred pain from pelvic inflammation. 1
• Ask about urinary frequency, urgency, decreased output, and hematuria. 1

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Diagnostic Testing Strategy

First-Line Laboratory Studies

• Complete blood count (leukocytosis suggests bacterial infection), electrolytes (hypokalemia, hyponatremia from diarrhea), creatinine (prerenal azotemia from dehydration). 1
• C-reactive protein or procalcitonin if infection versus inflammation is unclear. 1

Fecal Studies (Indicated When)

• Diarrhea >1 day with fever, bloody stools, severe dehydration, recent antibiotics, or systemic illness. 1
• Order stool culture, fecal leukocytes or lactoferrin, C. difficile toxin, and occult blood. 1, 3
• Fecal leukocytes, lactoferrin, or occult blood positivity suggests invasive bacterial pathogens (Shigella, Salmonella, Campylobacter). 1

Urinalysis

• Obtain urinalysis to differentiate urinary tract infection from dehydration-related symptoms (concentrated urine, elevated specific gravity). 1
• Pyuria and bacteriuria confirm UTI; absence suggests dehydration or referred pain. 1

Imaging (Reserved for Specific Indications)

• Plain abdominal radiography only if bowel obstruction or toxic megacolon suspected clinically. 1, 4
• CT abdomen/pelvis with IV contrast if peritoneal signs, severe systemic illness, or concern for abscess, perforation, or neutropenic enterocolitis. 1, 4, 3

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Immediate Management

Rehydration (Priority #1)

• Oral rehydration solution (Na 90 mM, K 20 mM, Cl 80 mM, HCO₃ 30 mM, glucose 111 mM) is superior to IV fluids for patients able to tolerate oral intake—less painful, safer, less costly. 1
• IV fluids (normal saline or lactated Ringer's) if unable to tolerate oral intake, severe dehydration, or hemodynamic instability. 1, 4
• Monitor urine output as rehydration marker; thirst decreases as patient rehydrates, protecting against overhydration. 1

Empirical Antibiotic Therapy (Selective Use Only)

• Do NOT routinely administer antibiotics for undifferentiated diarrhea. 1, 4
• Consider empirical fluoroquinolone (ciprofloxacin) or azithromycin if:
  • Traveler's diarrhea with moderate-to-severe symptoms (reduces duration from 3–5 days to 1–2 days). 1
  • Febrile dysentery (fever + bloody diarrhea + fecal leukocytes) suggesting invasive bacterial pathogen. 1
  • Immunocompromised state with systemic signs. 3
• Add metronidazole if C. difficile suspected (recent antibiotics, healthcare exposure). 1, 3
• Avoid antibiotics in suspected Shiga toxin-producing E. coli (STEC)—may induce toxin release and worsen hemolytic uremic syndrome. 1

Symptomatic Management

• Avoid anti-motility agents (loperamide) if fever, bloody diarrhea, or suspected invasive pathogen—may prolong infection and increase complications. 1, 3
• Provide analgesia (acetaminophen preferred; avoid NSAIDs in dehydration due to renal risk). 1, 4

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Red Flags Requiring Urgent Intervention

Signs of Complicated Course

• Peritoneal signs (rigidity, rebound tenderness) suggest perforation—immediate surgical consultation. 1, 4
• Fever + hypotension + altered mental status = septic shock—aggressive IV resuscitation, blood cultures, broad-spectrum antibiotics (piperacillin-tazobactam or carbapenem). 1, 3
• Massive dehydration, persistent vomiting preventing oral intake, or oliguria/anuria despite fluids. 1
• Hematochezia with hemodynamic instability. 1

Urinary Complications

• Acute urinary retention or severe dysuria may indicate bladder outlet obstruction from pelvic mass effect (abscess, fecal impaction). 1, 2
• Gross hematuria with abdominal pain raises concern for bladder injury or hemorrhagic cystitis—obtain CT cystography. 1

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Disposition and Follow-Up

Admission Criteria

• Severe dehydration unresponsive to oral rehydration, hemodynamic instability, altered mental status, or inability to tolerate oral intake. 1
• Febrile neutropenia, immunocompromised state, or suspected intra-abdominal abscess. 1, 3
• Peritoneal signs or imaging findings requiring surgical intervention. 1, 4

Outpatient Management (If Stable)

• Oral rehydration solution, dietary modifications (BRAT diet initially, advance as tolerated), and close follow-up in 24–48 hours. 1
• Empirical antibiotics if traveler's diarrhea or febrile dysentery (ciprofloxacin 500 mg PO BID × 3 days or azithromycin 500 mg PO daily × 3 days). 1
• Return precautions: worsening abdominal pain, high fever, bloody diarrhea, decreased urine output, dizziness, or confusion. 1

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Common Pitfalls to Avoid

• Do not delay rehydration while awaiting test results—volume resuscitation is therapeutic and diagnostic. 1, 4
• Do not assume urinary symptoms are always UTI—dehydration causes concentrated urine, dysuria, and frequency without infection. 1
• Do not overlook fecal impaction with overflow diarrhea—elderly, immobile, or opioid-using patients may present with "paradoxical diarrhea" around hard stool mass. 2
• Do not use anti-motility agents in bloody or febrile diarrhea—risk of toxic megacolon or prolonged pathogen shedding. 1, 3
• Do not attribute all symptoms to gastroenteritis—maintain suspicion for appendicitis, diverticulitis, inflammatory bowel disease, or ischemic colitis if atypical features present. 1, 4