Lesson
Define Anatomy and Physiology Before Severity
Complicated infection means extension beyond the hollow viscus into the peritoneum or another sterile abdominal space. Severity, acquisition, host reserve, and source-control delay are separate dimensions.
- Uncomplicated versus complicated
- Primary peritonitis
- Secondary peritonitis
- Tertiary peritonitis
- Sepsis risk
Is disease confined to the organ wall or extended into a sterile space?
Separate primary, secondary, and persistent or recurrent disease.
Shock and organ dysfunction set urgency, not the word complicated.
Resuscitation, imaging, antibiotics, and procedural planning move together.
Classify anatomic extension
Intramural inflammation is uncomplicated. Perforation, peritonitis, or abscess is complicated even if early physiology appears stable.
Separate peritonitis syndromes
SBP lacks a surgically correctable source. Secondary peritonitis follows perforation, ischemia, obstruction, trauma, or surgery. Tertiary disease persists or recurs after prior management.
Risk-stratify without outsourcing judgment
APACHE II is the preferred general adult severity score when one is used, while the WSES Sepsis Severity Score is an acceptable cIAI-specific alternative.
Treat sepsis in parallel
Resuscitation, cultures when actionable, active antibiotics, imaging, and procedural activation proceed together in shock or organ dysfunction.
Quick check
Lesson
Make Imaging Answer the Source-Control Question
Imaging must locate infection, define anatomy, reveal obstruction or ischemia, and create a safe path to drainage or surgery.
- CT
- Ultrasound
- MRI
- Pregnancy
- Repeat imaging
Define deep collections, leaks, obstruction, ischemia, and a drainage route.
Start biliary evaluation with stones, gallbladder, and duct anatomy.
Reduce radiation when appropriate without delaying dangerous disease.
Persistent illness requires a new image, not automatic extension.
Use CT for deep collections
Contrast-enhanced CT is preferred for most nonpregnant adults with suspected intra-abdominal abscess or postoperative collection.
Start biliary disease with ultrasound
Evaluate stones, gallbladder inflammation, and duct dilation first with ultrasound, then use HIDA, MRCP, CT, or endoscopic imaging for the remaining question.
Adapt pregnancy and pediatrics
Use ultrasound or MRI when diagnostically appropriate to avoid ionizing radiation, but do not delay diagnosis or source control of dangerous maternal or pediatric disease.
Repeat imaging when the course fails
Persistent fever, ileus, pain, leukocytosis, organ dysfunction, or abnormal drain output after treatment requires renewed CT or ultrasound evaluation.
Quick check
Lesson
Collect Specimens That Can Change the Regimen
Microbiology is most valuable when specimen quality, patient risk, and the decision it will inform are defined before collection.
- Source cultures
- Blood cultures
- Anaerobic transport
- Resistance history
- De-escalation
Aspirated fluid or tissue supports aerobic and anaerobic recovery.
Use physiology, immune status, cholangitis, and resistance risk.
Colonized tubing does not equal the active infected space.
Remove unnecessary resistant-pathogen and fungal coverage.
Culture the source
IDSA suggests intra-abdominal cultures during source-control procedures for complicated infection. Send adequate fresh fluid or tissue for aerobic and anaerobic culture.
Select blood cultures
Collect blood cultures with hypotension, tachypnea, delirium, other organ dysfunction, immune compromise, cholangitis, healthcare acquisition, or resistance concern.
Avoid low-quality specimens
Old drains and superficial swabs can reflect colonization. Document source, collection time, prior antibiotics, volume, and transport.
Narrow deliberately
Remove unnecessary anti-pseudomonal, enterococcal, MRSA, or antifungal therapy when source control, response, and cultures make it safe.
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Lesson
Stop Contamination Instead of Asking Drugs to Outrun It
Source control removes infected fluid or tissue, prevents ongoing contamination, relieves obstruction, and restores anatomy when possible.
- Drainage
- Debridement
- Repair
- Decompression
- Adequacy
Choose a safe definitive percutaneous or operative path.
Close the route that continues to seed the abdomen.
Debridement restores the conditions required for recovery.
Residual loculation, obstruction, or displaced drains preserve infection.
Control the lesion
Drain abscesses, debride necrosis, repair perforation or leak, remove infected material, and decompress obstruction according to anatomy.
Move urgently in instability
Septic shock, perforation, ischemia, uncontrolled leak, or cholangitis with organ dysfunction compresses the timeline for procedural control.
Use percutaneous drainage well
Plan a safe route, collect cultures, monitor output, flush and image when indicated, and define catheter removal or operative escalation criteria.
Audit adequacy
A completed procedure is not automatically adequate. Persistent leak, necrosis, undrained loculation, obstruction, or a displaced drain preserves infection.
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Lesson
Cover the Likely Ecology, Not Every Organism
Community acquisition usually requires enteric gram-negative, streptococcal, and anaerobic activity. Healthcare exposure, shock, colonization, and prior antibiotics can justify broader coverage.
- Enteric gram negatives
- Anaerobes
- Pseudomonas
- Enterococcus
- Candida
Community lower-GI disease needs gram-negative and anaerobic activity.
Healthcare exposure and prior isolates can justify Pseudomonas or ESBL activity.
Postoperative, transplant, immune, or culture context can make it relevant.
Strong host and source risk must support empiric antifungal therapy.
Focus community therapy
Ceftriaxone plus metronidazole or another appropriate focused regimen covers common enteric gram-negative and anaerobic pathogens when local susceptibility fits.
Broaden only for credible risk
Piperacillin-tazobactam, cefepime plus metronidazole, or meropenem can fit high-risk disease according to Pseudomonas, ESBL, and local ecology.
Add Enterococcus selectively
Routine community coverage is often unnecessary. Consider it in healthcare-associated, postoperative, transplant, immune-compromised, prior cephalosporin, or culture-supported disease.
Add Candida selectively
Reserve empiric antifungal therapy for selected critically ill patients with strong risk such as recurrent upper GI perforation, anastomotic leak, necrotizing pancreatitis, or supportive source evidence.
Quick check
Lesson
Turn Spectrum Into a Safe Exposure Plan
A regimen is complete only when its spectrum, dose, infusion, organ adjustment, interactions, toxicity, and de-escalation path fit the patient.
- Ceftriaxone plus metronidazole
- Piperacillin-tazobactam
- Cefepime plus metronidazole
- Meropenem
- Ertapenem
A common community pathway when ecology and organs fit.
Useful broad activity with resistance and organ boundaries.
Anaerobic activity must be added and kidney exposure followed.
Match meropenem or ertapenem to the actual resistance threat.
Build a common focused combination
Use ceftriaxone 2 g daily plus metronidazole 500 mg every 8 to 12 hours when community ecology, allergy, organs, and source fit.
Use broad single-agent therapy with boundaries
Piperacillin-tazobactam covers many gram-negatives, anaerobes, streptococci, and E. faecalis, but known difficult ESBL or carbapenemase phenotypes require another strategy.
Pair cefepime correctly
Add metronidazole because cefepime does not provide reliable Bacteroides coverage. Adjust cefepime for kidney function and neurotoxicity risk.
Steward carbapenems
Use meropenem for credible severe ESBL-risk disease. Use ertapenem only when Pseudomonas, Acinetobacter, and enterococcal activity are not needed.
Recalculate with organ change
Sepsis, resuscitation, dialysis, liver failure, weight, and improving kidney function can rapidly change exposure.
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Lesson
Let Source Control Start the Stop Clock
After adequate source control, modern evidence supports no more than four days for most cIAI. Persistent illness is a reason to investigate, not automatically extend.
- Four days
- Adequate control
- Failure imaging
- Oral step-down
- Stop ownership
Record when contamination stopped and drainage became adequate.
Most controlled cIAI needs no more than 96 hours afterward.
A route change completes the same total course.
Repeat imaging and reassess control before broadening or extending.
Replace the older long default
The 2024 SIS update recommends no more than four days, or 96 hours, after adequate source control. Initial sepsis alone does not require a longer course when control is achieved.
Do not let abscess mean fourteen days
A drained abscess with adequate control does not automatically require at least fourteen days. The anatomy and response, not the word abscess, determine exceptions.
Investigate failure
Persistent or recurrent evidence after 4 to 7 days requires CT or ultrasound, review of drain and operative findings, cultures, drug exposure, extra-abdominal infection, and noninfectious causes.
Use oral therapy inside the same course
Oral step-down can complete the short total duration when absorption, susceptibility, adherence, and stability are reliable. Route change does not restart the clock.
Document the stop owner
Name the source-control time, planned stop, culture review, route criteria, and failure pathway at the start of therapy.
Quick check
Lesson
Pair Antimicrobials With Definitive Biliary Care
Cholecystitis centers on gallbladder obstruction and cholecystectomy, while cholangitis centers on infected ductal obstruction and urgent decompression.
- Ultrasound
- Cholecystectomy
- Cholangitis
- ERCP
- Bile culture
Define gallbladder inflammation, stones, and duct dilation.
Early cholecystectomy is definitive when feasible.
Cholangitis requires urgent ERCP or another drainage route.
Cultures, clearance, obstruction, and response set the remaining course.
Manage cholecystitis definitively
Use early laparoscopic cholecystectomy when feasible. Antibiotics support complicated, infected, or systemic disease but do not remove the obstructed gallbladder.
Decompress cholangitis
Give prompt active antibiotics and arrange urgent ERCP or another drainage route according to severity, anatomy, and access.
Culture severe disease
Blood and bile cultures are useful in severe, healthcare-associated, instrumented, stented, transplant, or resistant-risk disease and should support narrowing.
Count duration from control
Drainage, blood-culture clearance, organism, abscess, persistent obstruction, and response determine the post-control course.
Quick check
Lesson
Separate Infected Ascites From a Surgical Abdomen
SBP is infected ascites without a surgically treatable source. Its PMN threshold, albumin strategy, secondary-peritonitis warning signs, and prophylaxis risks make it a distinct pathway.
- PMN at least 250
- Bedside inoculation
- Third-generation cephalosporin
- Albumin
- Secondary peritonitis
Neutrocytic ascites supports treatment before culture returns.
Immediate aerobic and anaerobic culture improves yield.
Use 1.5 g/kg on day 1 and 1 g/kg on day 3 when indicated.
Polymicrobial growth or poor response requires imaging and surgery review.
Diagnose from the PMN count
An ascitic PMN count at least 250 cells per cubic millimeter supports SBP treatment even if culture remains negative.
Improve culture yield
Inoculate ascitic fluid at bedside into aerobic and anaerobic blood culture bottles and send cell count, differential, protein, glucose, and LDH when secondary disease is a concern.
Treat and protect kidneys
Use cefotaxime or ceftriaxone for common community SBP while adapting to prior prophylaxis and healthcare resistance. Give albumin 1.5 g/kg on day 1 and 1 g/kg on day 3 when indicated.
Find secondary peritonitis
Polymicrobial culture, focal rigidity, free air, very high PMNs, high protein and LDH, low glucose, or poor response requires urgent imaging and surgical evaluation.
Use prophylaxis narrowly
Prior SBP, selected low-protein ascites with advanced disease, and cirrhosis with upper GI bleeding can qualify. Reassess resistance, C. difficile, adverse effects, and ongoing indication.
Quick check
Lesson
Keep the Plan Safe as the Patient Changes
Allergy labels, dynamic organ function, pregnancy, age, absorption, and discharge access can alter regimen safety without changing the need for prompt source control.
- Allergy phenotype
- Kidney function
- Liver disease
- Pregnancy and pediatrics
- Stewardship
Preserve safe beta-lactam options when the history allows.
Kidney trajectory, dialysis, liver reserve, and weight change exposure.
Adapt imaging and dosing without delaying source control.
Document spectrum, route, cultures, duration, and the failure pathway.
Clarify beta-lactam allergy
Distinguish intolerance, remote unknown reaction, immediate allergy, and severe delayed injury. Preserve appropriate cephalosporin or carbapenem options when safely possible.
Follow changing clearance
Use current kidney trajectory, urine output, dialysis timing, weight, liver reserve, and interacting nephrotoxins rather than one static admission estimate.
Treat pregnancy without delay
Choose ultrasound or MRI when appropriate and pregnancy-compatible drugs, but do not withhold necessary imaging, antibiotics, drainage, or surgery for maternal abdominal sepsis.
Use weight-based pediatric systems
Integrate age, weight, organ maturation, imaging sequence, dose ceilings, procedural timing, and family communication.
Close every antimicrobial indication
Document spectrum target, cultures, source control, dose, route, stop date, IV-to-oral criteria, and the clinician responsible for stopping or reassessing.
Quick check
Module test
Check the connections.
Each attempt draws 10 questions from the complete 172 question bank.
Each attempt draws a fresh set and rearranges the answer choices.
References
Current clinical foundation.
Lecture material was synthesized with the following contemporary guidance. Verify local policy and current guidance before applying clinical information.