Acute secondary bacterial peritonitis: pathophysiology, Causative organisms, Clinical findings differential diagnosis and treatment. Primary peritonitis. Detoxication, Gonococcal peritonitis. Tuberculous peritonitis. Granulomatous peritonitis. Peritoneal adhesions. Give all imp details about this topic explain well sorce : scwartz , doherty

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I have gathered extensive content from Schwartz's Principles of Surgery, Bailey & Love, and Sleisenger & Fordtran (which is co-authored by Doherty and is the closest match). Let me now compile the comprehensive answer.

Peritonitis: A Comprehensive Overview

Sources: Schwartz's Principles of Surgery (11th Ed.), Bailey & Love's Short Practice of Surgery (28th Ed.), Sleisenger & Fordtran's Gastrointestinal and Liver Disease

Classification of Peritonitis

Peritonitis is inflammation of the peritoneum and can be:

Localised or Diffuse
Acute or Chronic
Primary, Secondary, or Tertiary
Bacterial, Chemical, Granulomatous, or Ischemic

Causes include: bacterial (GI and non-GI), chemical (bile, barium), allergic (starch), traumatic (operative handling), ischemia (strangulated bowel), and miscellaneous (familial Mediterranean fever).

ACUTE SECONDARY BACTERIAL PERITONITIS

Definition

Secondary peritonitis occurs when the peritoneal cavity is contaminated following perforation or severe inflammation and infection of an intra-abdominal organ. Examples include appendicitis, perforated peptic ulcer, diverticulitis, and bowel ischemia.

Schwartz, p. 199

Pathophysiology

Routes of bacterial entry:

Transmural inflammation with luminal obstruction
Perforation of the GI tract
Bacterial translocation
Intestinal ischemia

The initial bacterial inoculum is determined by the normal flora of the involved GI segment. The large bowel harbors the richest flora; colonic perforation carries the highest morbidity.

Sleisenger, p. 640

Peritoneal Defense Mechanisms (overwhelmed in peritonitis):

Category	Mechanism
Removal	Bacterial clearance via diaphragm/thoracic duct
Leukocyte-attracting	ICAM-1, VCAM-1, mesothelial microvilli, neutrophil recruitment via omental HEVs
Killing	Macrophages (glutamate burst), neutrophils, opsonins (C3b, IgG), fibronectin, mast cell leukotrienes
Sequestration	Fibrin trapping, fibrinous adhesions, omental loculation

Within 6 minutes of intraperitoneal bacterial inoculation, bacteria are cultured in thoracic lymph; within 12 minutes, bacteremia is detectable. This diaphragmatic clearance is why Fowler's position (head-up, pelvis-down) was historically recommended.

Adjuvant substances that worsen outcome by interfering with bacterial killing: devitalized tissue, mucus, bile, hemoglobin, barium.

Peritoneal response:

The peritoneum becomes reddened, thickened, and velvety
Plaques of yellow/white fibrin form, causing bowel loops to adhere
Serous exudate, progressively turbid, eventually forming frank pus
Reflex ileus occurs
Bailey & Love, p. 1109

Tertiary peritonitis: When standard therapy fails, patients develop intra-abdominal abscess, anastomotic leak, or tertiary (persistent) peritonitis. This is more common in immunosuppressed patients. Organisms include E. faecalis/faecium, S. epidermidis, C. albicans, and P. aeruginosa - typically in combination. Mortality >50% even with appropriate therapy.

Schwartz, p. 199

Causative Organisms

The flora of surgical peritonitis rapidly simplifies after contamination. Key organisms:

Aerobes (gram-negative):

Escherichia coli - most common cause of bacteremia and death in experimental peritonitis
Klebsiella pneumoniae
Enterobacter spp.
Pseudomonas aeruginosa (nosocomial)

Aerobes (gram-positive):

Enterococcus spp.
Streptococcus spp.
Staphylococcus spp. (nosocomial)

Anaerobes:

Bacteroides fragilis - responsible for abscess formation
Clostridium spp.

Fungi:

Candida spp. - treat if septic shock, immunocompromised, or hospital-acquired; can safely observe in hemodynamically stable community-acquired cases

Microbial pattern in ruptured colonic diverticulitis:

Mixed aerobic + anaerobic flora: 74% of peritonitis, 77% of abscesses
Anaerobes alone: 18% of abscesses
Aerobes alone: 5% of abscesses

There is synergy between aerobic and anaerobic bacteria - E. coli drives mortality via bacteremia, while anaerobes (especially B. fragilis) drive abscess formation.

Sleisenger, p. 640-641

Clinical Findings

Symptoms:

Abdominal pain - hallmark; sudden onset with perforated viscus, insidious with localized infection
Character, location, radiation, change over time are diagnostically important
Nausea and vomiting (due to ileus)
Anorexia, malaise, lassitude

Signs:

Patient lies still - movement worsens pain
Fever 100°F or higher; tachycardia
Hypotension (late sign of sepsis)
Localised peritonitis: Involuntary guarding, rebound tenderness at affected area
Diffuse peritonitis: "Board-like" rigidity, absent bowel sounds, abdominal distension, Hippocratic facies
Loss of hepatic dullness on percussion = free air (pneumoperitoneum)
Pelvic peritonitis: deep tenderness on rectal or vaginal examination; referred shoulder tip pain (phrenic irritation, C5 dermatome)
In obese, elderly, immunosuppressed, CNS-injured, or intoxicated patients: signs may be markedly attenuated

Investigations:

FBC: leukocytosis (or leukopenia in overwhelming sepsis)
Serum lactate, electrolytes, LFTs, amylase/lipase
Erect CXR: Subdiaphragmatic gas = pneumoperitoneum; lateral decubitus film if patient too unwell to stand
CT abdomen (investigation of choice): Identifies source, free air, fluid collections, abscesses; guides drainage
Ultrasound: Less specific; useful for pelvic pathology, free fluid
Laparoscopy: If imaging inconclusive

Erect chest X-ray and CT showing pneumoperitoneum and sigmoid diverticulitis perforation

CT image demonstrating localised sigmoid diverticular perforation (arrow) - Bailey & Love, Fig. 65.7

Differential Diagnosis

Secondary peritonitis has numerous causes:

Category	Specific Cause
Upper GI	Perforated peptic ulcer (gastric or duodenal)
Hepatobiliary	Acute cholecystitis, bile duct perforation, biliary peritonitis
Pancreatic	Acute pancreatitis
Small bowel	Ischemia, obstruction with strangulation, Crohn's perforation
Large bowel	Diverticulitis, colonic perforation (obstructed/ischemic), appendicitis
Pelvic	PID, ruptured ectopic pregnancy, tubo-ovarian abscess
Post-surgical	Anastomotic leak, iatrogenic perforation
Vascular	Ruptured AAA (hemorrhagic peritonitis)
Autoimmune	SLE, endometriosis (peritoneal irritation but rarely clinical peritonitis)

Non-bacterial causes to exclude:

Hemorrhagic peritonitis - ruptured ectopic pregnancy, ovarian cyst, aneurysm; blood is highly irritating to peritoneum
Biliary peritonitis - sterile bile can be surprisingly asymptomatic; contaminated bile causes florid peritonitis
Sleisenger, p. 640

Treatment

The three pillars are: source control + antibiotic therapy + supportive care

1. General/Supportive Care

IV fluid resuscitation (correct fluid and electrolyte imbalance)
Urinary catheter + nasogastric drainage
Analgesia
Vital system support (ICU if needed)

2. Antibiotic Therapy

Community-acquired peritonitis: Coverage for susceptible gram-negative bacilli, strict anaerobes, and enterococci.

Hospital/healthcare-acquired peritonitis: Broader coverage for resistant organisms (MRSA, multiresistant Pseudomonas, Enterobacter, Enterococcus, Candida).

Regimen options (shown equivalent in multiple trials):

Second- or third-generation cephalosporins
Broad-spectrum beta-lactams (monotherapy as effective as beta-lactam + aminoglycoside)
Fluoroquinolones + metronidazole
Carbapenems (for healthcare-associated/resistant)
Aminoglycosides are now rarely needed given availability of broad-spectrum agents with less nephrotoxicity

Duration: The STOP-IT trial showed 4 ± 1 days post-source-control was equivalent to antibiotics until fever/leukocytosis resolved (~8 days).

Sleisenger, p. 641-642

Candida: Treat only if: septic shock, immunocompromised state, or hospital-acquired infection.

3. Surgical Intervention (Source Control)

Antibiotics without source control cannot cure surgical peritonitis
Requires: Resection or repair of diseased organ; debridement of necrotic tissue; peritoneal lavage
Intra-abdominal abscesses: Majority drained percutaneously under CT guidance; surgery reserved for multiple abscesses, proximity to vital structures, or ongoing enteric leak
Catheter left until output <10 mL/day and cavity collapse confirmed; short antibiotic course (3-5 days) during drainage

Outcomes:

Effective source control + antibiotics: mortality ~5-6%; response rate 70-90%
Failure of source control: mortality >40%
Schwartz, p. 199-200

DETOXICATION (PERITONEAL CLEARANCE)

The peritoneum has a remarkable ability to clear bacteria and toxins:

Diaphragmatic lymphatics: The primary clearance site - bacteria pass through diaphragmatic stomata into the thoracic duct, reaching systemic circulation within 6-12 minutes
Phagocytosis by peritoneal macrophages and recruited neutrophils, aided by complement (C3b), IgG, and fibronectin as opsonins
Omental loculation: The "policeman of the abdomen" - the omentum physically walls off infection, limiting spread
Fibrin deposition traps bacteria but also leads to adhesion formation

Blockade of the thoracic duct in animal models decreases bacteremic episodes but increases mortality (due to liver necrosis from endotoxin accumulation), confirming that systemic clearance via the diaphragm is protective.

Sleisenger, p. 640-641

PRIMARY PERITONITIS (Spontaneous Bacterial Peritonitis - SBP)

Definition

Peritonitis without a known surgical source - microbial invasion of the peritoneal cavity via hematogenous dissemination or direct inoculation into pre-existing ascitic fluid.

Schwartz, p. 199

Who is at risk?

Cirrhosis with ascites (most common)
Nephrotic syndrome with ascites
Patients on peritoneal dialysis (CAPD)
Children (pneumococcal primary peritonitis - historically, now rare)

Organisms

Without CAPD: E. coli, K. pneumoniae, S. pneumoniae (gram-negatives predominate)
With CAPD: Gram-positives dominate (S. epidermidis, other skin flora); less commonly gram-negative bacilli, Pseudomonas, fungi, Mycobacterium tuberculosis
SBP is invariably monomicrobial; polymicrobial infection suggests secondary peritonitis

Diagnosis

Paracentesis: >250 neutrophils/mL in ascitic fluid
Culture is negative in up to 60% of cases with clinical SBP
A floridly positive Gram stain suggests secondary bacterial peritonitis (high bacterial load)
Runyon criteria used to differentiate SBP from secondary peritonitis (total protein, LDH, glucose on ascitic fluid)

Treatment

No surgical intervention required
Empirical antibiotics immediately (before culture results):
- Third-generation cephalosporin (e.g., cefotaxime) - first-line (avoids aminoglycoside renal toxicity)
- Alternatives: amoxicillin/clavulanic acid, ciprofloxacin
- CAPD peritonitis: intraperitoneal route preferred; vancomycin or cephalosporin empirically; catheter removal for fungal or recurrent bacterial infections
Duration: 14-21 days typically
Indwelling devices (CAPD catheter) may need removal for recurrent infections
Bailey & Love, p. 1111; Schwartz, p. 198-199

Primary Pneumococcal Peritonitis

Incidence has declined greatly; now rare
Affects children, especially girls (route: vagina → Fallopian tubes) or via blood-borne spread from respiratory/middle-ear infection
Also in nephrotic syndrome and cirrhosis in children
Onset: Sudden; pain lower abdomen; temperature ≥39°C; frequent vomiting; after 24-48h, profuse diarrhea (characteristic); increased urinary frequency
Signs: diffuse peritonism but less prominent than with perforated viscus
Causative organism confirmed on culture; must exclude secondary cause before labelling as primary peritonitis
Bailey & Love, p. 1111

GONOCOCCAL PERITONITIS (Fitz-Hugh-Curtis Syndrome)

Pathogenesis

Pelvic infection via the Fallopian tubes accounts for a high proportion of non-gastrointestinal peritonitis
Chlamydia spp. and Neisseria gonorrhoeae are the most common offending organisms
These organisms cause thinning of cervical mucus, allowing bacteria to pass into the uterus and oviducts, causing pelvic inflammatory disease (PID)
Fitz-Hugh-Curtis syndrome: Transperitoneal spread of gonococcal/chlamydial organisms to the liver capsule, causing perihepatitis with formation of violin-string scar tissue on Glisson's capsule
10-40% of women with untreated lower-tract gonococcal infection progress to PID (salpingitis, endometritis, oophoritis, peritonitis)
Bailey & Love, p. 1110; Sleisenger, p. 643 (Box 39.2)

Clinical Features

Abdominal pain (may mimic acute abdomen)
Cervical motion tenderness, adnexal tenderness
In Fitz-Hugh-Curtis: right upper quadrant pain (perihepatitis), pleuritic component
Vaginal discharge

Treatment

Antibiotic therapy for PID (dual therapy covering gonorrhea and chlamydia per current guidelines)
No surgical intervention unless complicated (tubo-ovarian abscess requiring drainage)

TUBERCULOUS PERITONITIS

Epidemiology & Risk Factors

Uncommon form of extrapulmonary tuberculosis caused by Mycobacterium tuberculosis
Increased risk in: HIV infection, cirrhosis, diabetes mellitus, underlying malignancy
Sleisenger, p. 643

Pathogenesis

Spread from: tuberculous lymph node, intestinal focus, or infected Fallopian tube
Haematogenous seeding can also occur

Clinical Forms

Exudative (wet) type: Ascites predominates (straw-coloured exudate)
Plastic (dry) type: Dense fibrinous adhesions, omental thickening, bowel obstruction; insidious onset with abdominal pain, weight loss, distension
Fibrotic/fixed (mixed) type

Clinical Features

Abdominal pain, night sweats, malaise, weight loss
Ascites (may be loculated)
Can present as a pelvic mass mimicking ovarian cancer (elevated CA-125)
May be clinically indistinguishable from acute bacterial peritonitis in its acute form
Bailey & Love, p. 1111

Diagnostic Investigations

Test	Finding
Ascitic fluid protein	High (>25-30 g/L)
Ascitic fluid glucose	Low
SAAG	Low (<1.1 g/dL) in non-cirrhotic patients
Ascitic WBC	Elevated, lymphocytic predominance (>40%)
AFB smear	Often negative
Culture	May take 4-8 weeks
Adenosine deaminase (ADA)	Elevated - high sensitivity and specificity for TB peritonitis; differentiates from carcinomatosis
Xpert MTB/RIF (PCR)	Rapid, noninvasive; emerging role
ELISPOT	Novel noninvasive test
QuantiFERON Gold	Poor specificity for active disease, especially in BCG-vaccinated populations
CT/Ultrasound	Ascites, lymphadenopathy, diffuse peritoneal/omental/mesenteric thickening
Laparoscopy + biopsy	Near-100% sensitive; couples macroscopic appearances (caseating nodules) with histology

Distinguishing feature: Afebrile patients with lymphocytic ascites → malignancy (10x more common than TB); febrile patients → TB Cancer: cytology positive >90% → avoid laparoscopy; if cytology negative → laparoscopy (near 100% sensitive for TB)

Treatment

Medical (first-line):
- 2 months: Isoniazid + Rifampicin + Pyrazinamide + Ethambutol
- Then 4 months: Isoniazid + Rifampicin
- Total: 6-month course
- Drug-resistant strains may require extended or modified regimens
- Monitor for hepatotoxicity, especially in cirrhotic patients
Surgical: Only for complications (intestinal obstruction - though may respond to anti-TB therapy without surgery)
Nutritional and hydration support
Sleisenger, p. 643-644; Bailey & Love, p. 1111

GRANULOMATOUS PERITONITIS

Definition

Peritoneal inflammation characterized by granuloma formation. Often has a chronic, indolent course.

Causes

Tuberculous peritonitis (caseating granulomas) - most common infective cause
Starch/Talc peritonitis: Historically from surgical glove powder (cornstarch or talc)
- Cornstarch potentiates wound infection, forms peritoneal adhesions, induces granulomatous peritonitis, and serves as a carrier of latex allergen
- Glove powder granulomas can mimic peritoneal carcinomatosis on imaging
- Sleisenger, p. 643
Fungal infections (Histoplasma, Coccidioides, Cryptococcus) - especially in AIDS/immunocompromised
Sarcoidosis
Crohn's disease
Foreign body (suture material, barium from previous contrast studies)
Parasitic (e.g., schistosomiasis)

Clinical Features

Abdominal pain (may be sudden or insidious depending on cause)
Ascites with lymphocytic predominance
Constitutional symptoms (fever, weight loss)

Diagnosis

CT: peritoneal thickening, ascites, nodular deposits (indistinguishable from carcinomatosis)
Laparoscopy + biopsy with histology is definitive
AFB staining and culture for TB
Ascitic ADA for TB

Treatment

Directed at the underlying cause:

TB: anti-tuberculous regimen as above
Starch peritonitis: supportive; steroids in severe cases
Fungal: amphotericin B or azole antifungals
Foreign body: surgical removal when feasible

PERITONEAL ADHESIONS

Definition

Fibrous bands of scar tissue connecting surfaces within the peritoneal cavity that are normally separate.

Pathogenesis

After peritoneal injury (surgical, inflammatory, ischemic), fibrin is deposited as part of the healing response (sequestration mechanism). Normally, fibrin is lysed by peritoneal fibrinolytic activity. When fibrinolysis is inadequate (e.g., due to ongoing ischemia, infection, or foreign material), fibrin organizes into permanent fibrous adhesions.

Factors promoting adhesion formation:

Peritoneal infection or inflammation
Surgical trauma (drying, handling, devascularization of peritoneum)
Foreign bodies (sutures, mesh, glove powder, barium)
Ischemia
CAPD peritonitis (repeated infections lead to sclerosing encapsulating peritonitis / "abdominal cocoon")

Clinical Consequences

Small bowel obstruction (most common consequence; adhesions account for ~60% of all SBO cases)
Chronic abdominal pain
Infertility (in females - tubo-ovarian adhesions from PID or pelvic surgery)
Difficulty at re-operative surgery
Sclerosing encapsulating peritonitis (abdominal cocoon): Complication of repeated CAPD peritonitis; loss of surface area for effective dialysis; associated with repeated infections
- Sleisenger, p. 643

Prevention

Gentle tissue handling during surgery
Use of adhesion barriers (sodium hyaluronate/carboxymethylcellulose membrane, e.g., Seprafilm) in high-risk cases
Peritoneal lavage to remove blood, fibrin, and contamination
Minimally invasive (laparoscopic) surgery produces fewer adhesions than open surgery
Heparin addition to dialysis bags in CAPD peritonitis may reduce fibrin and postinfection adhesions (though urokinase showed no benefit)
- Sleisenger, p. 643

Treatment of Adhesion-Related SBO

Conservative: IV fluids, NG decompression, monitoring
Surgical: Adhesiolysis (open or laparoscopic) for complete obstruction or failure of conservative management; risk of enterotomy and recurrent adhesions

Summary Table: Key Comparisons

Feature	Primary (SBP)	Secondary Bacterial	Tuberculous	Granulomatous
Source	No surgical source	Viscus perforation/inflammation	M. tuberculosis	TB, fungi, starch, FB
Organisms	Monomicrobial	Polymicrobial (aerobes + anaerobes)	M. tuberculosis	Varies
Ascites WBC	>250 PMNs	High PMNs	Lymphocytic >40%	Lymphocytic
ADA	Normal	Normal	Elevated	Elevated (TB)
Gram stain	Negative (low bacterial load)	Positive/florid	Negative	Negative
Surgery needed	No	Yes (source control)	Only complications	Only complications
Treatment	Antibiotics 14-21d	Source control + antibiotics 4d	6-month anti-TB	Cause-directed

Sources:

Schwartz's Principles of Surgery, 11th Ed., pp. 198-200
Bailey & Love's Short Practice of Surgery, 28th Ed., pp. 1109-1113
Sleisenger & Fordtran's Gastrointestinal and Liver Disease, pp. 639-647

Tumors of the peritoneum and retropetorneum. Source :- doherty Nd scwartz

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Tumors of the Peritoneum and Retroperitoneum

Sources: Schwartz's Principles of Surgery (11th Ed.), Bailey & Love's Short Practice of Surgery (28th Ed.), Sleisenger & Fordtran's Gastrointestinal and Liver Disease

CLASSIFICATION OVERVIEW

Category	Peritoneum	Retroperitoneum
Primary benign	Peritoneal inclusion cysts	Retroperitoneal cysts, benign lipoma
Primary malignant	Mesothelioma, primary peritoneal carcinoma, DSRCT	Retroperitoneal sarcoma (liposarcoma, leiomyosarcoma)
Secondary malignant	Peritoneal carcinomatosis, pseudomyxoma peritonei	Lymphoma, germ cell tumors, metastatic cancer
Other	Desmoid tumors, GIST	Retroperitoneal fibrosis (tumor-like)

PART I: TUMORS OF THE PERITONEUM

A. PRIMARY TUMORS OF THE PERITONEUM

Primary peritoneal tumors are rare and arise from the mesothelium of the peritoneum.

Bailey & Love, p. 1112

1. PERITONEAL MESOTHELIOMA

Epidemiology

65-70% of all mesotheliomas arise in the pleura; 25% arise in the peritoneum
Most peritoneal mesotheliomas are malignant
Associated with asbestos exposure (families of asbestos workers also at risk)
Detected typically 35-40 years after initial asbestos exposure
Patients with malignant peritoneal mesothelioma often harbor sporadic and occasionally germline BRCA-associated protein-1 (BAP-1) mutations
Sleisenger, p. 646
Bailey & Love: has a predilection for the pelvic peritoneum; equally lethal as pleural mesothelioma

Histological Variants

Malignant (epithelioid) - most common; aggressive
Well-differentiated papillary mesothelioma - indolent course
Multicystic mesothelioma - indolent course
Sarcomatoid - worst prognosis

Clinical Features

Diffuse abdominal pain and distension
Ascites (malignant mesothelial cells occasionally found on ascitic fluid analysis)
Weight loss
Diagnosis usually made at laparotomy or laparoscopy

Diagnosis

CT/MRI: peritoneal thickening, nodular deposits, ascites
Ascitic fluid cytology (occasionally positive)
Laparoscopy + biopsy - definitive
BAP-1 mutation testing

Treatment

Best treated in a multidisciplinary setting
Cytoreductive surgery (CRS) + HIPEC (Heated Intraperitoneal Chemotherapy)
- HIPEC agents: cisplatin/Adriamycin/mitomycin-C
- 5-year survival: 29-70% with CRS + HIPEC
Systemic chemotherapy: Cisplatin + pemetrexed
Sleisenger, p. 646 (Table 39.1)

2. PRIMARY PERITONEAL CARCINOMA

Resembles high-grade serous ovarian carcinoma histologically but arises from the peritoneal surface without clear ovarian primary
Treated similarly to ovarian cancer

Treatment (Table 39.1, Sleisenger)

Systemic: Taxane + carboplatin (neoadjuvant or adjuvant)
Surgery: Optimal cytoreduction
Regional: Intraperitoneal chemotherapy (cisplatin/paclitaxel) ± HIPEC (cisplatin/carboplatin)

3. DESMOPLASTIC SMALL ROUND CELL TUMOR (DSRCT)

Rare, aggressive sarcoma affecting the peritoneum, primarily in young males
Harbors EWS-WT1 gene fusion (translocation-associated sarcoma)
Treatment:
- Systemic: Cyclophosphamide, doxorubicin, vincristine alternating with ifosfamide and etoposide; autologous stem cell rescue; whole abdominal radiation
- Optimal cytoreductive surgery + HIPEC (cisplatin)
Sleisenger, p. 646 (Table 39.1)

B. SECONDARY PERITONEAL TUMORS (PERITONEAL CARCINOMATOSIS)

Definition & Epidemiology

Peritoneal carcinomatosis refers to malignant nodules on the surface of the peritoneum. It is common and normally arises in conjunction with:

Ovarian malignancy
Malignancy in an organ of the mesenteric domain (colorectal, appendiceal, gastric, pancreatic)
Any peritoneal surface can be involved
Sometimes the omentum is diffusely involved, forming a mass termed an "omental cake"
Bailey & Love, p. 1112

Clinical Features

Symptoms are mainly related to the primary pathology
With considerable tumour burden: palpable mass, substantial ascites, abdominal distension
Subacute intestinal obstruction

Diagnosis

CT or MRI is usually diagnostic (shows peritoneal nodules, omental thickening, ascites)
Histological or cytological confirmation is essential to distinguish from:
- Peritoneal TB (laparoscopy if cytology negative)
- Pseudomyxoma peritonei
Serum CA-125 (elevated in ovarian + peritoneal primaries but also TB)
Ascitic cytology (>90% positive if peritoneal metastases present)

Treatment

If curative resection is feasible: Primary tumour resection + peritonectomy + HIPEC
- HIPEC: highly concentrated, heated (41-42°C) chemotherapy delivered directly into the abdomen for 90 minutes after cytoreductive surgery
- Particularly valuable in pseudomyxoma peritonei (standard of care in carefully selected patients at specialist centres - Sugarbaker technique)
In majority of patients: Treatment is palliative
- Subacute obstruction: intestinal bypass or defunctioning stoma
- Malignant ascites: drained externally or via peritoneovenous shunt (LeVeen shunt)
Bailey & Love, p. 1112-1113

C. PSEUDOMYXOMA PERITONEI (PMP)

Definition

Not a diagnosis in itself but a syndrome of mucinous ascites primarily associated with appendiceal epithelial neoplasms; can also occur with ovarian, pancreatic, colorectal, and gastric mucinous tumors.

Sleisenger, p. 645-646

Pathogenesis

Appendiceal mucinous neoplasms develop peritoneal dissemination
Histologic origin of mucinous ascites predicts outcome:
- Low-grade appendiceal mucinous neoplasms (formerly cystadenoma/mucocele) - better prognosis
- High-grade (adenocarcinoma, goblet cell carcinoma, signet ring cell) - worse prognosis

Clinical Features

Presenting symptoms: Painless abdominal distension (typical)
Progressive accumulation of jelly-like mucinous material

Diagnosis

Definitive: characteristic jelly-like material encountered at laparotomy or laparoscopy
CT: "scalloping" of visceral surfaces by mucinous deposits; omental caking
Differentiate low-grade from high-grade histology (guides prognosis and adjuvant therapy)

Treatment

Standard of care: Cytoreductive surgery (CRS) + HIPEC (mitomycin-C for low-grade; mitomycin-C ± systemic chemotherapy for high-grade)
Parietal and visceral peritonectomies + intraperitoneal heated chemotherapy (42°C, usually mitomycin-C)
Right hemicolectomy can be avoided in patients in whom complete cytoreductive surgery is possible without removing the colon (nodal metastases rare in low-grade)
Can be performed laparoscopically when disease detected early and is low volume
Previously considered a morbid surgery; now at high-volume centres, morbidity and mortality are similar to any major open GI procedure
Schwartz, p. 1368; Sleisenger, p. 645-646

Histological Subtype	Systemic Therapy	Surgery	HIPEC
Low-grade appendiceal	None	Optimal cytoreduction	Mitomycin-C
High-grade appendiceal	Fluoropyrimidine, oxaliplatin, irinotecan, anti-EGFR, anti-VEGF	Optimal cytoreduction	Mitomycin-C
Colorectal carcinoma	Fluoropyrimidine, oxaliplatin, irinotecan, bevacizumab, cetuximab	Optimal cytoreduction	Mitomycin-C/oxaliplatin
Ovarian	Taxane/carboplatin	Optimal cytoreduction	HIPEC (cisplatin)

D. PERITONEAL INCLUSION CYSTS

Benign cysts lined by peritoneal mesothelium
Can arise at any location of the peritoneum (parietal or visceral surface)
Gradually expand; rarely rupture
Most are asymptomatic - identified incidentally on cross-sectional imaging
Loose association with ovarian malignancy - MRI of ovaries advisable in premenopausal women
Treatment (if symptomatic): image-guided drainage, deroofing, or excision; recurrence rates are high
Bailey & Love, p. 1112

PART II: TUMORS OF THE RETROPERITONEUM

Anatomy Recap

The retroperitoneum is bound by:

Anteriorly: Peritoneum
Posteriorly: Iliopsoas and lumbar muscles
Superiorly: Diaphragm
Inferiorly: Levator ani muscles

Three spaces: anterior pararenal, perirenal, and posterior pararenal. Tumors tend to expand anteriorly toward the peritoneal cavity given the rigidity of posterior margins.

Schwartz, p. 1589

A. RETROPERITONEAL SARCOMA

Epidemiology

Most retroperitoneal tumors are malignant; ~one-third are soft tissue sarcomas
~1000 new cases of retroperitoneal sarcoma diagnosed annually in the United States
Accounts for 10-15% of all adult soft tissue sarcomas
~two-thirds are high grade (grade 2 or 3)
Sarcomas: 50-60% originate in extremity; 15% in retroperitoneum; 19% in trunk; 9% head and neck
Schwartz, p. 1582

Common Histologies in the Retroperitoneum

Liposarcoma - most common retroperitoneal sarcoma
Leiomyosarcoma - second most common

Other retroperitoneal tumors (differential):

Primary germ cell tumors
Lymphoma
Metastatic testicular cancer

Soft Tissue Sarcoma Subtypes (>70 histologic subtypes total)

Historically most common (adults, excluding Kaposi sarcoma): malignant fibrous histiocytoma (28%), liposarcoma (15%), leiomyosarcoma (12%), synovial sarcoma.

Molecular pathogenesis (Schwartz classification):

Group	Mechanism	Examples
1	Specific translocations	Ewing's (EWS-FLI1), myxoid liposarcoma (TLS-CHOP), alveolar RMS (PAX3-FHKR), synovial sarcoma (SS18-SSX), DSRCT (EWS-WT1), clear cell sarcoma (EWS-ATF1)
2	Gene amplification	Amplification-associated sarcomas
3	Oncogenic mutations	GIST (KIT, PDGFRA mutations)
4	Complex genomic rearrangements	Older patients, pleomorphic cytology, p53 dysfunction

Risk Factors for Sarcoma

Radiation exposure (post-radiation sarcoma)
Occupational chemical exposure
Chronic lymphedema (Stewart-Treves syndrome - lymphangiosarcoma after axillary dissection; average survival 19 months)
Trauma - no causal relationship established; trauma often merely reveals a preexisting tumor
Schwartz, p. 1595-1596

Clinical Presentation

Retroperitoneal sarcomas present as large masses - 70% are >10 cm at diagnosis
Do not produce symptoms until large enough to compress/invade contiguous structures
When symptomatic: abdominal pain, early satiety, obstructive GI symptoms
Must exclude lymphoma symptoms: fever, night sweats; testicular examination in men (germ cell tumors)
Schwartz, p. 1582

Staging (AJCC 8th Edition - revised)

Subsites now created separately (retroperitoneum as distinct subsite from extremity)
Histologic grade is the most important prognostic factor:
- Grade 1 (well differentiated): 5-year survival 90%; metastasis in 5-10%
- Grade 2 (moderately differentiated): 5-year survival 70%; metastasis in 25-30%
- Grade 3 (poorly differentiated): 5-year survival 40%; metastasis in 50-60%
Grading based on: cellularity, differentiation, pleomorphism, necrosis (<50% vs ≥50%), mitoses per HPF
Size criteria (trunk/extremity): T1 <5cm; T2 5-10cm; T3 10-15cm; T4 >15cm
Lymph node metastases rare overall but higher for: epithelioid sarcoma, pediatric RMS, clear cell sarcoma, synovial sarcoma, angiosarcoma
Schwartz, p. 1595-1596

Diagnostic Workup

History: Exclude lymphoma (B symptoms), check lactate dehydrogenase (elevated = suggests lymphoma), β-hCG/AFP (germ cell tumor)
CT abdomen/pelvis with contrast (investigation of choice):
- Defines tumor extent and relationship to vascular structures for surgical planning
- Can distinguish well-differentiated vs dedifferentiated liposarcoma
- Evaluates liver (metastases), peritoneum (discontiguous disease), kidneys (function)
Thoracic CT: Evaluate for lung metastases (11% of patients present with synchronous metastatic disease)
Angiography/MR arteriography-venography: When involvement of critical vascular structures suspected
CT-guided core needle biopsy: For tissue diagnosis; well-differentiated liposarcoma may be diagnosed by CT alone (negative biopsy should NOT delay operative intervention)

Schwartz, p. 1582

Treatment

Surgery (cornerstone):

Complete surgical resection is the most effective treatment for primary or recurrent retroperitoneal sarcoma
En bloc resection often necessitates sacrificing contiguous structures:
- Colon, kidney, spleen, pancreas, psoas muscle, small bowel, inferior vena cava, aorta
In a review of 25 patients with major vascular involvement: postoperative morbidity 36%, mortality 4%; vessel patency >88%; vascular resection is treatment of choice when major vessels are involved
Goal is R0 (microscopically negative margins) - local control and survival rates are favorable with tumor-free margins
Extended procedures are feasible and safe at experienced centres
Schwartz, p. 1582-1583

Radiation Therapy:

Debate exists on optimal sequencing (pre- vs post-operative)
Preoperative RT (50 Gy) vs postoperative RT (66 Gy) - randomized trial (NCI Canada/Canadian Sarcoma Group):
- Wound complications higher pre-op (35% vs 17%)
- Late toxicity (fibrosis, joint stiffness, edema) more common post-op (48% vs 32%)
- Recurrence and progression-free survival similar in both groups
Brachytherapy: Shorter treatment (4-6 days vs 4-6 weeks for external beam); catheters spaced at 1-cm increments, loaded after 5th postoperative day with iridium-192 (42-45 Gy)
IMRT: Delivers radiation more precisely, minimizing dose to surrounding tissues
Schwartz, p. 2051-2062

Systemic Therapy (chemotherapy):

Doxorubicin-based regimens are the backbone
Limited efficacy in retroperitoneal sarcoma compared to extremity sarcomas
Histology-specific approaches being developed

B. GASTROINTESTINAL STROMAL TUMORS (GIST) - Special Sarcoma Category

Molecular Biology

Arise from interstitial cells of Cajal (pacemaker cells of GI tract)
>80% harbor activating mutations in KIT (c-KIT) proto-oncogene
~10-15% harbor mutations in PDGFR-alpha (PDGFRA)
Small fraction: KIT/PDGFRA wild-type (e.g., SDH-deficient, NF1-associated)

Clinical Presentation

Most common sites: stomach (50-60%), small intestine (20-30%), colon/rectum
Symptoms: GI bleeding, abdominal mass, obstruction, or incidental finding

Treatment of GIST

Localized disease - Surgery:

Wide local excision with negative margins; no lymphadenectomy required (nodal metastases rare)

Advanced/Metastatic disease - Targeted therapy:

Imatinib (Gleevec): First-line tyrosine kinase inhibitor (TKI) targeting KIT/PDGFR

FDA approved; dramatically improved survival

Sunitinib: Second-line; multi-kinase inhibitor (targets VEGFR, PDGFRA, KIT, FLT3)

Phase 3 trial: median time to progression 27.3 weeks vs 6.4 weeks with placebo
Adverse effects: diarrhea, fatigue, nausea, hand-foot reaction, hypertension, cardiotoxicity, hypothyroidism
FDA approved in 2006 for imatinib-resistant/intolerant GIST

Regorafenib: Third-line; structurally unique multi-kinase inhibitor (KIT, PDGFR)

Phase 3 trial: median PFS 4.8 months vs 0.9 months with placebo
Other options after regorafenib: sorafenib, dasatinib, nilotinib

Multidisciplinary/Surgery for advanced disease:

Surgery for isolated disease progression during imatinib therapy
Surgical resection of residual imatinib-sensitive metastatic disease: progression-free survival in 70-96%

Postoperative (adjuvant) imatinib:

ACOSOG trial: evaluated 1 year of postoperative imatinib in high-risk resectable GIST (large size or high mitotic count); demonstrated improved recurrence-free survival
Schwartz, p. 2303-2315

C. SCLEROSING MESENTERITIS (Mesenteric Tumors/Fibrosis)

Rare disorder: idiopathic fibrosis of the mesentery affecting hollow viscera and mesenteric vessels
Spectrum: mesenteric lipodystrophy (localised) → mesenteric panniculitis (diffuse) → sclerosing mesenteritis (fibrosis)
Aetiology: Unknown; may be related to: prior abdominal surgery, autoimmune disease, paraneoplastic syndrome, previous infection (typhoid, TB, influenza, rheumatic fever), vascular insult
Demographics: White patients, 50-70 years; male predominance

Clinical Features:

Abdominal pain (most common), nausea/vomiting, weight loss, anorexia, altered bowel habits
Up to 50% have an abdominal mass that transmits aortic pulsations

CT Findings:

Soft tissue mass with higher density than normal mesenteric tissue
"Tumour pseudocapsule" - hypodense zone around fibrotic mass
"Fat ring sign" - area of preserved fat near mesenteric vessels coursing through areas of fibrosis
May be calcified

Treatment:

Pathologic confirmation required (laparoscopic or open biopsy)
Medical therapy: corticosteroids, tamoxifen, colchicine (for IgG4-related disease)
Schwartz, p. 1587

D. RETROPERITONEAL FIBROSIS (Ormond's Disease) - Tumour-like Condition

Fibroinflammatory process encasing the retroperitoneal structures
Causes: Idiopathic (majority - often IgG4-related), drugs (methysergide, beta-blockers), malignancy (lymphoma, carcinoid), infections, aortic aneurysm (periaortitis)
Manifestations: Ureteral obstruction (hydronephrosis), vascular compression
Treatment: Steroids; tamoxifen; surgical ureterolysis for obstruction
Schwartz, p. 1589-1562

E. RETROPERITONEAL CYSTS AND BENIGN TUMORS

Primary retroperitoneal mucinous cystadenoma (rare)
Benign lipoma
Mature teratoma (in young patients - germ cell origin)
Lymphangioma/cystic hygroma

PART III: OMENTUM AND MESENTERY - TUMORS

Omentum Tumors

The omentum (the "policeman of the abdomen") has primarily a defensive role. Acquired omental disorders include:

Omental torsion and infarction (pseudotumour on imaging)
Omental GIST - rare; treat as per standard GIST protocol
Metastatic omental involvement (omental cake) - from GI, ovarian, or other peritoneal malignancies
Primary omental sarcoma - extremely rare

Mesenteric Cysts

Arise from mesenteric lymphatics (lymphangioma) or mesothelium
Present as abdominal mass ± pain
Treatment: surgical excision

Mesenteric Tumors

GISTs can arise in the mesentery (extragastrointestinal stromal tumor)
Desmoid tumors: Associated with Gardner syndrome (FAP); locally aggressive but do not metastasize; treated with surgery, NSAIDs, tamoxifen, imatinib
Carcinoid (NET): Often cause a desmoplastic mesenteric reaction with tethering of bowel loops

SUMMARY TABLE: Key Peritoneal/Retroperitoneal Tumors

Tumor	Origin	Key Feature	Treatment
Peritoneal mesothelioma	Mesothelium	Asbestos exposure; BAP-1 mutation	CRS + HIPEC (cisplatin/ADM/MMC)
Pseudomyxoma peritonei	Appendix (mostly)	Jelly-like mucinous ascites	CRS + HIPEC (MMC)
Peritoneal carcinomatosis	Secondary (ovary, colon, etc.)	Omental cake; malignant ascites	CRS + HIPEC if resectable; palliative otherwise
DSRCT	Peritoneum (young males)	EWS-WT1 fusion	CRS + HIPEC + systemic chemo
Retroperitoneal liposarcoma	Retroperitoneal fat	Most common RP sarcoma; >10cm at diagnosis	En bloc resection ± RT
Retroperitoneal leiomyosarcoma	Smooth muscle (IVC, etc.)	Second most common; IVC often involved	En bloc resection ± RT
GIST	Interstitial cells of Cajal	KIT/PDGFRA mutation	Surgery ± imatinib/sunitinib/regorafenib
Desmoid	Musculoaponeurotic fibroblasts	FAP association; locally aggressive	Surgery, tamoxifen, imatinib
Sclerosing mesenteritis	Mesenteric fat	"Fat ring sign" + pseudocapsule on CT	Steroids, tamoxifen

Sources:

Schwartz's Principles of Surgery, 11th Ed., Chapter 35 (pp. 1557-1590) and Chapter 36 (pp. 1567-1590)
Bailey & Love's Short Practice of Surgery, 28th Ed., Chapter 65 (pp. 1112-1113)
Sleisenger & Fordtran's Gastrointestinal and Liver Disease, Chapter 39 (pp. 640-647, Table 39.1)

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