Colitis → Perforated Abdomen (Sepsis)

Management of Colitis vs Perforated Abdomen in the Septic Patient

Start broad-spectrum antibiotics after blood cultures are drawn, give a full loading dose in sepsis, and escalate to perforated-abdomen coverage if there is free air, diffuse peritonitis, or abscess on imaging. Adjust doses for renal function once the patient is stabilized.

Empiric antibiotics: Colitis with sepsis (no perforation)

Option	Regimen and dose	Coverage	Renal adjustment summary
Single agent	Piperacillin-tazobactam 4.5 g IV every 6 to 8 hours. Extended infusion is preferred in severe sepsis when feasible.	Enteric gram-negatives, anaerobes, enterococci, Pseudomonas.	CrCl greater than 40 mL/min: full dose. CrCl 20 to 40 mL/min: 3.375 g every 6 hours. CrCl less than 20 mL/min: 2.25 g every 6 to 8 hours.
Combination	Cefepime 2 g IV every 8 hours + Metronidazole 500 mg IV every 8 hours. Alternative: Ceftriaxone 2 g IV daily + Metronidazole 500 mg IV every 8 hours (community-acquired, lower Pseudomonas risk).	Cefepime combo adds Pseudomonas coverage; ceftriaxone combo covers typical enteric pathogens and anaerobes.	Cefepime adjust by CrCl (see renal table). Ceftriaxone: no renal change (monitor in severe hepatic plus renal dysfunction). Metronidazole: generally no change; consider every 12 hours if CrCl less than 10.
Beta-lactam allergy	Ciprofloxacin 400 mg IV every 12 hours + Metronidazole 500 mg IV every 8 hours. Alternative: Moxifloxacin 400 mg IV daily (less Pseudomonas coverage).	Enteric gram-negatives and anaerobes; no enterococcal coverage.	Ciprofloxacin: CrCl 30 to 50 mL/min every 12 hours; CrCl less than 30 mL/min every 24 hours. Metronidazole: see note above.

Pearl: give a full loading dose up front in sepsis, then apply renal adjustment based on estimated creatinine clearance.

Empiric antibiotics: Perforated abdomen or surgical abdomen

Option	Regimen and dose	Coverage	Renal adjustment summary
Single agent	Piperacillin-tazobactam 4.5 g IV every 6 to 8 hours (extended infusion when feasible), or Meropenem 1 g IV every 8 hours.	Broad enteric gram-negatives, anaerobes, enterococci, Pseudomonas; carbapenem adds ESBL coverage.	Zosyn per CrCl (see renal table). Meropenem: CrCl 26 to 50 mL/min every 12 hours; CrCl 10 to 25 mL/min 500 mg every 12 hours; CrCl less than 10 mL/min 500 mg every 24 hours.
Combination	Cefepime 2 g IV every 8 to 12 hours + Metronidazole 500 mg IV every 8 hours.	Pseudomonas plus anaerobes; add-ons below for MRSA or Candida risks.	Cefepime by CrCl; Metronidazole generally no change.

Urgent source control is critical: surgical consultation for repair, washout, or drainage should proceed in parallel with antibiotics and resuscitation.

Add-on coverage

Indication	Agent and dose	Notes	Renal adjustment summary
MRSA risk factors (hospital-acquired, prior MRSA, post-op GI infection)	Vancomycin 15 to 20 mg per kg IV every 8 to 12 hours	Use AUC-guided or level-guided dosing; combine with base regimen.	Adjust interval and dose per creatinine clearance and serum levels.
High Candida risk (immunocompromised, upper GI perforation with shock, recurrent IAI, yeast on peritoneal Gram stain)	Fluconazole: load 800 mg IV once, then 400 mg IV daily	Consider an echinocandin if unstable or non-albicans risk; de-escalate when species known.	CrCl 50 mL/min or less: reduce maintenance to 200 mg daily.

Renal dosing quick guide

Drug	Sepsis loading / standard	CrCl greater than 40	CrCl 20 to 40	CrCl less than 20	Hemodialysis
Piperacillin-tazobactam	Load 4.5 g IV once	4.5 g every 6 to 8 h	3.375 g every 6 h	2.25 g every 6 to 8 h	2.25 g every 8 h + 0.75 g after HD
Meropenem	1 g IV	1 g every 8 h	1 g every 12 h	500 mg every 24 h	500 mg every 24 h after HD
Cefepime	2 g IV	2 g every 8 to 12 h	2 g every 12 to 24 h	1 g every 24 h	1 g after HD
Ceftriaxone	2 g IV	2 g daily	No renal change; monitor if combined severe hepatic plus renal dysfunction			Not dialyzable; give on schedule
Metronidazole	500 mg IV	500 mg every 8 h	500 mg every 8 h	Consider 500 mg every 12 h	Give after HD on dialysis days
Ciprofloxacin	400 mg IV	400 mg every 12 h	400 mg every 12 h	400 mg every 24 h	Give after HD
Vancomycin	15 to 20 mg per kg IV	Dose per AUC or trough protocol; extend interval with lower CrCl				Redose per levels post-HD
Fluconazole	800 mg load	400 mg daily	If CrCl 50 or less: 200 mg daily		Give post-HD; consider 200 mg daily

Estimate creatinine clearance with Cockcroft-Gault using actual body weight unless patient is very obese, where adjusted body weight may be used per local protocol.

Diagnostic work-up and septic shock management

Phase	Checklist
Initial evaluation	CBC, CMP, magnesium, phosphorus, coagulation panel; serum lactate and repeat within 2 to 4 hours if elevated. Two sets of blood cultures before antibiotics; urinalysis as indicated. Stool tests: C. difficile PCR or toxin, bacterial culture; ova and parasite if travel or exposure risks. CT abdomen and pelvis with IV contrast if feasible to localize inflammation, abscess, or free air. Early surgical consult if peritonitis, free air, uncontrolled sepsis, or evolving organ failure.
Ongoing assessment	Trend lactate and blood gases; monitor urine output and hemodynamics. Reassess abdomen frequently; consider repeat imaging if no improvement in 24 to 48 hours. Send peritoneal fluid for Gram stain and culture if drains placed or ascites present.
Septic shock bundle	Crystalloid 30 mL per kg within first 3 hours (adjust for fluid intolerance). Start norepinephrine to maintain MAP 65 or higher if hypotension persists after fluids. Give broad-spectrum antibiotics within 1 hour of shock recognition; de-escalate when culture data return. Source control: operative repair, washout, or percutaneous drainage without delay when indicated. Consider stress-dose steroids if refractory shock per local protocol.

Duration of therapy is typically 4 to 7 days after adequate source control and clinical improvement; extend if bacteremia with difficult organisms or persistent uncontrolled source.

Disclaimer: This quick guide does not replace clinical judgment. Follow local antibiograms, stewardship policies, and pharmacy dosing protocols.