Bacterial Peritonitis Diagnosis (RCSI 2024)

Leading the world to better health  Diagnosis and Management of Bacterial Peritonitis Professor Karen Burns, Consultant Clinical Microbiologist Beaumont Hospital & Dept. of Clinical Microbiology, RCSI  RCSI Royal College of Surgeons in Ireland Coláiste Ríoga na Máinleá...

Leading the world to better health  Diagnosis and Management of Bacterial Peritonitis Professor Karen Burns, Consultant Clinical Microbiologist Beaumont Hospital & Dept. of Clinical Microbiology, RCSI  RCSI Royal College of Surgeons in Ireland Coláiste Ríoga na Máinleá in Éirinn SESSION ID: GIHEPMicroL6 Diagnosis and Management of Bacterial Peritonitis Class: Year 2 24/25 Course: Undergraduate Medicine Lecturer: Professor Karen Burns Date: 18th September 2024 LEARNING OUTCOMES At the end of this session you should be able to: 1. Classify bacterial peritonitis 2. Describe the clinical features of bacterial peritonitis 3. Discuss the aetiology of bacterial peritonitis 4. Choose the appropriate empiric antimicrobials to treat bacterial peritonitis 5. Discuss other aspects of management of bacterial peritonitis  ANATOMY OF THE ABDOMEN Peritoneum: continuous serous membrane lining the abdominal cavity and covering the abdominal viscera Divided into – Parietal peritoneum (attached to abdominal wall) – Visceral peritoneum (wrapped around visceral organs) – Peritoneal cavity (potential space between parietal and visceral peritoneum) – contains a small amount of sterile lubricating fluid secreted by mesothelium, allowing layers to glide easily over one another ANATOMY OF THE ABDOMEN  ANATOMY OF THE ABDOMEN Organs may be INTRA-peritoneal or RETRO- peritoneal Intraperitoneal organs are enveloped by visceral peritoneum, which covers the organ both anteriorly and posteriorly – Stomach, liver and spleen are all intraperitoneal Retroperitoneal organs are only covered in parietal peritoneum, which only covers their anterior surface Oesophagus, rectum, kidneys, pancreas, ascending and descending colon ANATOMY OF THE ABDOMEN PERITONITIS Definition: Localised or generalised inflammation of the peritoneum resulting in an exudate, which rapidly becomes purulent – Localised – e.g. inflamed appendix – Generalised – e.g. perforated colon Arises from contamination of the peritoneal cavity, which is normally sterile Microorganisms (bacteria, fungi) Irritating chemicals (e.g. bile, urine, gastric content, blood) Both PERITONITIS - CLASSIFICATION Primary/Spontaneous Bacterial Peritonitis Secondary Peritonitis Peritoneal dialysis-associated peritonitis PRIMARY/SPONTANEOUS BACTERIAL PERITONITIS (SBP) No obvious source May be seen in patients with pre-existing ascites (e.g. in chronic liver disease) Does not involve disruption of abdominal wall and intra-abdominal organs No macroscopic defect in the gastro-intestinal tract SECONDARY PERITONITIS Secondary to intra- abdominal lesions/spillage Perforation of an organ, tumour Penetrating injury to abdominal wall Acute pancreatitis Post-procedure (e.g. anastomotic leak following bowel resection, iatrogenic perforation following colonoscopy)  PERITONITIS If you don’t send a specimen of peritoneal fluid to microbiology – you won’t know what microorganism(s) are causing the infection or what antimicrobials they are resistant or susceptible to  PERITONEAL DIALYSIS (PD)- ASSOCIATED PERITONITIS PD (Tenckhoff) catheter provides a portal of entry for organisms into the normally sterile peritoneum ‘Touch-contamination’ or exit-site infection Less commonly, intra- abdominal source PERITONITIS: CLINICAL FEATURES ‘Peritonism’ = signs & symptoms of peritonitis Symptoms: Abdominal pain, feeling “bloated” & generally unwell, +/- nausea/vomiting/anorexia Abdominal pain may radiate to shoulders or back, and may be worse on movement Fever Peritonitis may be localised or generalised 32 YEAR OLD FEMALE WITH TENDERNESS AND GUARDING ON PALPATION OF RIGHT ILIAC FOSSA, ULTRASOUND SHOWS ACUTE APPENDICITIS A. Primary peritonitis B. Secondary localised peritonitis C. Secondary generalised peritonitis D. Peritoneal-dialysis peritonitis PERITONITIS: CLINICAL FEATURES Patient may have features of sepsis – fever, tachycardia, hypotension, oliguria, mottled skin On examination: usually presents as an acute abdomen – acute abdominal pain, – (rebound) tenderness to palpation, – distension, – rigid abdomen, – guarding, – percussion tenderness PERITONITIS: CLINICAL FEATURES If PD peritonitis, symptoms may also include: – Cloudy dialysis fluid – White flecks, strands or clumps (fibrin) in the dialysis fluid – Infection due to anaerobes uncommon in this scenario PERITONITIS: AETIOLOGY PRIMARY/SBP Remember: No obvious source Infection of ascitic fluid Risk factors include cirrhosis of the liver Majority are mono-microbial Usually aerobic bacteria – Enterobacterales: E. coli, K. pneumoniae – Pseudomonas aeruginosa – S. pneumoniae, GAS, enterococci, Staphylococcus aureus – Anaerobes rarely PERITONITIS: AETIOLOGY SECONDARY PERITONITIS Occurs secondary to spillage of enteric (gastrointestinal/bowel/gut) or genitourinary tract microorganisms into the sterile peritoneal cavity Majority of infections are polymicrobial Causative microorganisms include aerobic & anaerobic bacteria, and Candida species that reflect the usual flora of the area of diseased GI/GU tract Enterobacterales Enterococci, streptococci Bacteroides spp., Prevotella spp., other anaerobes Candida spp.  PERITONITIS: AETIOLOGY PERITONEAL DIALYSIS (PD)-ASSOCIATED PERITONITIS Skin flora: – S. aureus, CoNS Less commonly: – GI flora: E. coli, Pseudomonas aeruginosa Transmural: GI bacteria migrate through the bowel wall – Anaerobes rarely CASE STUDY 45 year-old female attends ED complaining of 2 day history of epigastric pain, worsening in severity Has been taking NSAID 3 times daily (TDS) for ‘pulled muscle’ for the past week On examination: – Heart rate 130bpm – Blood pressure 100/60 mmHg – Severe abdominal tenderness, diffusely, with guarding What is the likely diagnosis? WHAT IS THE LIKELY DIAGNOSIS?  PERITONITIS: DIAGNOSIS Clinical signs & symptoms Laboratory – Routine bloods (FBC, renal profile, liver function tests, coagulation profile, CRP) – Amylase (to outrule pancreatitis) – Lactate – Blood for group and save/crossmatch (in case requires surgery and/or blood transfusion) – Venous/arterial blood gas if shock/ischaemia – Procalcitonin (PCT) if pancreatitis Would expect elevated CRP, WCC, indicating inflammation/infection  PERITONITIS: DIAGNOSIS Microbiology Blood cultures Urine MC&S Peritoneal fluid specimen (depends on likely aetiology): – Intra-operative specimen of pus or fluid (secondary peritonitis) Gram stain and culture Organism may fail to culture if prior antimicrobials received or delayed receipt in laboratory – Ascitic tap (primary peritonitis/SBP) Cell count, Gram stain and culture – Peritoneal dialysis (PD) fluid Cell count, Gram stain and culture PERITONITIS: DIAGNOSIS Radiology: Abdominal X-ray (erect) – May miss small amounts of free air CT abdomen & pelvis – Radiation, contrast Ultrasound scan – No contrast used – Identifies free fluid – Can be done at bedside ERECT CXR - FREE AIR UNDER THE DIAPHRAGM ERECT CXR - FREE AIR UNDER THE DIAPHRAGM PFA – RIGLER’S SIGN PFA – RIGLER’S SIGN Free intra-abdominal gas adjacent to a gas-filled loop of bowel: both sides of the bowel wall are well-defined ABDOMINAL CT ABDOMINAL CT BACK TO OUR CASE… Routine bloods performed – Elevated white cell count (WCC) and CRP – Elevated lactate Microbiological investigations: – Blood and urine cultures sent Radiology: – Erect CXR demonstrated air under hemi-diaphragm – Diagnosis of perforated duodenal ulcer made on abdominal CT scan What is your next step? WHAT IS YOUR NEXT STEP? MANAGEMENT OF PERITONITIS Initially Rest the bowel - NPO Large-bore IV cannula Analgesia IV fluids Further management depends on clinical presentation – may need surgical exploration If sepsis/septic shock, supportive treatment in critical care setting may be required (oxygen, ventilation, inotropes, dialysis) MANAGEMENT OF SECONDARY PERITONITIS 1) Empiric antimicrobials (Local Beaumont guidelines – check the app) – Choice based upon likely microorganisms and clinical scenario (community versus hospital-acquired infection) – Empiric = peritoneal fluid culture & susceptibility result not yet available: Community-acquired: 2nd generation cephalosporin (cefuroxime) + aminoglycoside (gentamicin) + metronidazole OR Hospital-acquired: β-lactam/β-lactamase inhibitor combination (piperacillin-tazobactam) + aminoglycoside (gentamicin) – Adding an empiric antifungal agent (caspofungin or fluconazole) may be recommended in certain scenarios – check local guidelines and discuss with clinical microbiologist MANAGEMENT OF SECONDARY PERITONITIS Rationale: – Cefuroxime covers aerobic Gram positive cocci and Enterobacterales (not Pseudomonas), but does not have anaerobic cover, so metronidazole is added to provide the anaerobic cover – Pip/tazo covers aerobic Gram positive cocci and Gram negative bacilli (including Pseudomonas) and also has good anaerobic cover, so no need to add metronidazole – Gentamicin is second agent added to provide Gram negative cover, just in case of resistance to pip/tazo or cefuroxime (given for 48 hours while waiting for peritoneal fluid C&S). Gentamicin does not provide anaerobic cover, which is provided by pip/tazo or metronidazole WHICH OF THESE ANTIMICROBIALS COVERS ANAEROBIC BACTERIA? A. Co-amoxiclav B. Metronidazole C. Piperacillin-tazobactam D. All of the above  A LITTLE REVISION… Broad-spectrum Narrow spectrum Piperacillin-tazobactam: Penicillin G, effective against some Gram amoxicillin; active positive cocci (GPC), Gram against GPC, some negative bacilli (GNB) GNC including Pseudomonas spp. & NOT suitable for anaerobes empiric therapy of infections which are Co-amoxiclav: effective likely to be against some GPC, GNB such polymicrobial, or as E. coli, (approx 50% caused by Gram- resistant), H. influenzae (not a negative bacilli typical pathogen in peritonitis) & anaerobes START SMART – THEN FOCUS Aim of empiric treatment: cover the likely microorganisms for the clinical scenario Peritonitis: cover bowel/enteric microorganisms: Gram negatives and anaerobes Check lab results for any prior positive microbiology/similar previous episodes (especially with SBP or PD-peritonitis) Once results available (blood cultures, peritoneal fluid C&S) – Target/rationalise antimicrobial therapy – Resistant microorganisms – escalate – Susceptible microorganisms – de-escalate If you don’t send a specimen of peritoneal fluid to microbiology, you won’t learn the causative microorganisms and their susceptibility results and you can’t rationalise empiric therapy MANAGEMENT OF SECONDARY PERITONITIS 2) Source control – remove source of contamination and repair any anatomical or functional defect – Drainage of abscess (may be done in operating theatre, or under image-guidance in interventional radiology department) – Appendicectomy, bowel resection, repair of perforation If laparotomy being performed, peritonitis may be evident as purulent or faecal material in peritoneal cavity – Needs washout or ‘lavage’ – Specimen of fluid/faecal material should be sent promptly to Microbiology for culture and susceptibility testing MANAGEMENT OF PRIMARY PERITONITIS (SBP) OR PD PERITONITIS Typically monomicrobial infection, but you need to also exclude occult perforation (polymicrobial infection) Specimen of peritoneal fluid: – SBP = ascitic tap or diagnostic paracentesis of ascitic fluid for cell count, Gram stain, culture & susceptibility – PD-peritonitis = PD fluid for cell count, Gram stain, culture and susceptibility and PD catheter exit site swab Empiric antimicrobials: – IV route for primary peritonitis (SBP) – PD peritonitis may be treated via intraperitoneal (IP) route – PD catheter allows direct administration into peritoneal cavity PD catheter may need removal or exchange  COMPLICATIONS OF BACTERIAL PERITONITIS Bloodstream infection (BSI) Sepsis/septic shock Localised abscess/collection Adhesions – Fibrous scar tissue as a result of peritoneal inflammation – Can result in abnormal attachments between visceral peritoneum of adjacent organs, or between visceral and parietal peritoneum. – May cause pain, volvulus, intestinal obstruction 65 YEAR OLD FEMALE WITH ASCITES, CONFUSION AND FEVER, AND GENERALISED ABDOMINAL TENDERNESS. PAST HISTORY OF ALCOHOLIC LIVER CIRRHOSIS. A. Spontaneous bacterial peritonitis B. Secondary localised peritonitis C. Secondary generalised peritonitis D. Peritoneal-dialysis peritonitis  1 2 4 5 6 7 8 3 SAMPLE PSA MCQ: Case presentation: A 76-year-old male presents to the ED with acute abdominal A.Change to co- pain and fever. He is taken to theatre where amoxiclav he is diagnosed with peritonitis secondary B.Change to piperacillin- to a perforated diverticulum. He undergoes tazobactam a peritoneal washout and bowel resection and is commenced on empiric cefuroxime C.Change to vancomycin and metronidazole. Peritoneal pus is sent to and metronidazole the microbiology laboratory D.Continue cefuroxime Investigations: Peritoneal pus sent to the and metronidazole microbiology laboratory. Culture result E.Continue cefuroxime reports Pseudomonas aeruginosa after 24 and stop hours, susceptibilities are pending metronidazole Question: What is the most appropriate course of management for this patient now?  SUMMARY Peritonitis to be suspected based on signs & symptoms of an acute abdomen Peritonitis may be classified into primary (SBP), secondary, and peritoneal dialysis (PD)-associated peritonitis Causative microorganisms vary depending on underlying aetiology – Mainly bacteria, but fungi (Candida species) in some cases Diagnosis of peritonitis requires a clinical examination, laboratory, microbiological and radiological investigations Send specimen of peritoneal fluid to microbiology! Peritonitis is usually managed with a combination of empiric antimicrobial therapy PLUS source control (drainage/surgery, repair of perforation) Choice of empiric antimicrobial should cover likely microorganisms. Include anaerobic cover for secondary peritonitis. Thank you