ABCRS cheat sheet

Colon cancer staging: T1 invades submucosa, T2 muscularis propria, T3 through muscularis into subserosa/pericolic fat, T4a penetrates visceral peritoneum, T4b directly invades another organ.

Nodal staging: N1 = 1-3 nodes, N2 = 4 or more nodes; at least 12 lymph nodes should be examined for adequate staging.

Stage II high-risk features (adjuvant chemo considered): T4, perforation, obstruction, poorly differentiated histology, lymphovascular or perineural invasion, fewer than 12 nodes, positive margins.

Stage III colon cancer: adjuvant FOLFOX for 3-6 months or CAPOX; duration shortened to 3 months for low-risk (T1-3 N1) disease.

Rectal cancer: neoadjuvant chemoradiation for T3/T4 or node-positive disease; total mesorectal excision is the standard surgical technique.

Lynch syndrome (HNPCC): Amsterdam/Bethesda criteria, mismatch repair deficiency or MSI-high; universal IHC screening recommended for all colorectal cancers.

CEA is used for postoperative surveillance, not screening; rising CEA after resection warrants imaging to evaluate for recurrence.

Metastatic colorectal cancer: KRAS/NRAS and BRAF mutation status and MSI status guide anti-EGFR therapy and immunotherapy decisions.

Ulcerative colitis: continuous mucosal inflammation from rectum proximally, confined to colon; Crohn disease: skip lesions, transmural, any GI segment, perianal involvement.

Toxic megacolon: colonic dilation >6 cm with systemic toxicity; contraindicates colonoscopy and antimotility agents; requires IV fluids, steroids, and surgical consultation.

Acute severe ulcerative colitis (Truelove-Witts): 6 or more bloody stools/day plus fever, tachycardia, anemia, or elevated ESR; IV corticosteroids first line.

Crohn disease: smoking worsens disease; ulcerative colitis: smoking may be protective but is not recommended.

Perianal Crohn disease: MRI pelvis and exam under anesthesia for characterization; seton drainage preferred over fistulotomy to preserve continence.

Pouchitis after IPAA: responds to antibiotics (ciprofloxacin or metronidazole); chronic pouchitis may require biologics or Crohn-directed therapy.

Surveillance: colitis-associated dysplasia screening with chromoendoscopy; 8-10 years after diagnosis for extensive colitis.

Biologic therapy: anti-TNF agents require latent TB screening; avoid live vaccines on immunosuppression.

Hemorrhoids: internal above dentate line (painless bleeding), external below (painful if thrombosed); grade I-III treated with banding, grade IV with surgery.

Thrombosed external hemorrhoid: excision within 72 hours of onset relieves pain; after 72 hours, conservative management.

Anal fissure: posterior midline most common; chronic fissure shows sentinel tag, hypertrophied papilla, exposed internal sphincter fibers.

Fissure treatment ladder: fiber and sitz baths, topical nitrates or calcium channel blockers, botulinum toxin injection, then lateral internal sphincterotomy.

Abscess: incision and drainage is definitive; antibiotics alone are inadequate. Fistulotomy is avoided in acute abscess unless superficial.

Fistula-in-ano: Goodsall rule - anterior tracts exit radially, posterior tracts curve to posterior midline; Parks classification by sphincter relationship.

Fistula management: seton for high/complex tracts or Crohn disease; advancement flap or LIFT for sphincter-preserving repair.

Anal cancer: squamous cell carcinoma; chemoradiation (Nigro regimen, 5-FU plus mitomycin) is first-line; abdominoperineal resection for salvage.

Fecal incontinence workup: history, endoanal ultrasound, anorectal manometry, pudendal nerve studies; rule out impaction and sphincter defect.

Sphincter defect >120 degrees or >25-30% of circumference on ultrasound may benefit from overlapping sphincteroplasty.

Sacral neuromodulation: test phase then implant; indicated for refractory fecal incontinence and some constipation; contraindicated in pregnancy.

Obstructed defecation: defecography or MR defecography identifies rectocele, intussusception, or paradoxical puborectalis contraction.

Biofeedback and pelvic floor physical therapy are first-line for dyssynergic defecation.

Rectal prolapse: full-thickness prolapse in elderly patients often treated with perineal (Altemeier) or abdominal rectopexy; assess for concomitant incontinence.

Slow-transit constipation: confirmed with transit study (radiopaque markers or scintigraphy); surgery reserved for refractory, well-selected cases.

Pudendal neuralgia: pain relieved by sitting, worsened by sitting on hard surfaces; diagnosed by pudendal nerve block.

Colon injury: primary repair acceptable for most low-energy civilian injuries; diversion (colostomy) for destructive injuries, shock, or contamination.

Damage control laparotomy: temporary abdominal closure, correction of acidosis, hypothermia, and coagulopathy; planned re-exploration.

Splenic injury: nonoperative management for hemodynamically stable patients; embolization for active blush; splenectomy for instability.

Small bowel injury: repair or resection with primary anastomosis; avoid anastomosis in severe shock or peritonitis.

Diaphragmatic injury: left side more common with blunt trauma; laparoscopy or thoracoscopy for occult injury in penetrating thoracoabdominal wounds.

Mesenteric ischemia: SMA embolus classically at middle colic branch; CT angiography is diagnostic; laparotomy for infarction or peritonitis.

Acute appendicitis: laparoscopic appendectomy standard; antibiotics alone for uncomplicated cases in selected patients; interval appendectomy controversial.

Large bowel obstruction with competent ileocecal valve risks closed-loop perforation at cecum; cecal diameter >9-12 cm is a warning sign.

Enhanced recovery after surgery (ERAS): preoperative counseling, no routine mechanical bowel prep, carbohydrate loading, multimodal analgesia, early feeding, early ambulation.

VTE prophylaxis: low-molecular-weight heparin or unfractionated heparin for colorectal surgery; extend 4 weeks after cancer resection.

Surgical antibiotic prophylaxis: administer within 60 minutes before incision; redose for long cases or major blood loss.

Sepsis: recognize with SOFA/qSOFA; sepsis bundle includes cultures, broad-spectrum antibiotics within 1 hour, 30 mL/kg crystalloid for hypotension or lactate ≥4.

Acute respiratory distress syndrome: Berlin criteria - onset within 1 week, bilateral opacities, not cardiogenic, PaO2/FiO2 ≤300; low tidal volume ventilation 6 mL/kg.

Perioperative cardiac risk: revised cardiac risk index (RCRI) predicts major cardiac events; consider functional capacity and surgery-specific risk.

Ostomy care: stoma should be matured at initial surgery; high-output ileostomy (>1-1.5 L/day) risks dehydration and electrolyte loss.

Nutrition: early enteral feeding preferred; immunonutrition considered in malnourished patients undergoing major GI surgery.

Laparoscopic colectomy: oncologic equivalence to open surgery for colon cancer; conversion rates higher with obesity, adhesions, and locally advanced tumors.

Pneumoperitoneum: typically 12-15 mmHg CO2; physiologic effects include hypercapnia, decreased venous return, and increased airway pressures.

Robotic surgery advantages: articulating instruments, tremor filtration, three-dimensional visualization; useful in narrow pelvis for rectal cancer and prostate surgery.

Laparoscopic entry: open (Hasson) technique reduces major vascular and bowel injury versus closed Veress needle entry.

Single-incision and natural orifice approaches: cosmetic benefit but increased hernia risk and technical difficulty; not standard of care for all cases.

Intraoperative CO2 embolism: sudden hypotension, arrhythmia, and desaturation; treat by desufflation, 100% oxygen, left lateral decubitus position.

Enhanced recovery and ERAS protocols complement minimally invasive surgery, reducing length of stay.

Simulation-based training and credentialing are recommended before independent laparoscopic practice.

Informed consent: requires disclosure of diagnosis, proposed treatment, alternatives, and material risks; assess patient comprehension and voluntariness.

Belmont Report principles: respect for persons, beneficence, and justice; governs human subjects research.

Institutional review board (IRB) approval required before human subjects research; exempt and expedited categories exist.

Conflict of interest: disclose financial relationships with industry; manage and recuse when appropriate.

Levels of evidence: systematic reviews of RCTs highest; case reports and expert opinion lowest.

Sensitivity = true positives / (true positives + false negatives); specificity = true negatives / (true negatives + false positives).

Positive predictive value depends on disease prevalence; negative predictive value also varies with prevalence.

Professionalism: maintain competence, honesty in reporting, patient confidentiality (HIPAA), and appropriate boundaries.

Colon cancer staging: T1 invades submucosa, T2 muscularis propria, T3 through muscularis into subserosa/pericolic fat, T4a penetrates visceral peritoneum, T4b directly invades another organ.

Nodal staging: N1 = 1-3 nodes, N2 = 4 or more nodes; at least 12 lymph nodes should be examined for adequate staging.

Stage II high-risk features (adjuvant chemo considered): T4, perforation, obstruction, poorly differentiated histology, lymphovascular or perineural invasion, fewer than 12 nodes, positive margins.

Stage III colon cancer: adjuvant FOLFOX for 3-6 months or CAPOX; duration shortened to 3 months for low-risk (T1-3 N1) disease.

Rectal cancer: neoadjuvant chemoradiation for T3/T4 or node-positive disease; total mesorectal excision is the standard surgical technique.

Lynch syndrome (HNPCC): Amsterdam/Bethesda criteria, mismatch repair deficiency or MSI-high; universal IHC screening recommended for all colorectal cancers.

CEA is used for postoperative surveillance, not screening; rising CEA after resection warrants imaging to evaluate for recurrence.

Metastatic colorectal cancer: KRAS/NRAS and BRAF mutation status and MSI status guide anti-EGFR therapy and immunotherapy decisions.

Ulcerative colitis: continuous mucosal inflammation from rectum proximally, confined to colon; Crohn disease: skip lesions, transmural, any GI segment, perianal involvement.

Toxic megacolon: colonic dilation >6 cm with systemic toxicity; contraindicates colonoscopy and antimotility agents; requires IV fluids, steroids, and surgical consultation.

Acute severe ulcerative colitis (Truelove-Witts): 6 or more bloody stools/day plus fever, tachycardia, anemia, or elevated ESR; IV corticosteroids first line.

Crohn disease: smoking worsens disease; ulcerative colitis: smoking may be protective but is not recommended.

Perianal Crohn disease: MRI pelvis and exam under anesthesia for characterization; seton drainage preferred over fistulotomy to preserve continence.

Pouchitis after IPAA: responds to antibiotics (ciprofloxacin or metronidazole); chronic pouchitis may require biologics or Crohn-directed therapy.

Surveillance: colitis-associated dysplasia screening with chromoendoscopy; 8-10 years after diagnosis for extensive colitis.

Biologic therapy: anti-TNF agents require latent TB screening; avoid live vaccines on immunosuppression.

Hemorrhoids: internal above dentate line (painless bleeding), external below (painful if thrombosed); grade I-III treated with banding, grade IV with surgery.

Thrombosed external hemorrhoid: excision within 72 hours of onset relieves pain; after 72 hours, conservative management.

Anal fissure: posterior midline most common; chronic fissure shows sentinel tag, hypertrophied papilla, exposed internal sphincter fibers.

Fissure treatment ladder: fiber and sitz baths, topical nitrates or calcium channel blockers, botulinum toxin injection, then lateral internal sphincterotomy.

Abscess: incision and drainage is definitive; antibiotics alone are inadequate. Fistulotomy is avoided in acute abscess unless superficial.

Fistula-in-ano: Goodsall rule - anterior tracts exit radially, posterior tracts curve to posterior midline; Parks classification by sphincter relationship.

Fistula management: seton for high/complex tracts or Crohn disease; advancement flap or LIFT for sphincter-preserving repair.

Anal cancer: squamous cell carcinoma; chemoradiation (Nigro regimen, 5-FU plus mitomycin) is first-line; abdominoperineal resection for salvage.

Fecal incontinence workup: history, endoanal ultrasound, anorectal manometry, pudendal nerve studies; rule out impaction and sphincter defect.

Sphincter defect >120 degrees or >25-30% of circumference on ultrasound may benefit from overlapping sphincteroplasty.

Sacral neuromodulation: test phase then implant; indicated for refractory fecal incontinence and some constipation; contraindicated in pregnancy.

Obstructed defecation: defecography or MR defecography identifies rectocele, intussusception, or paradoxical puborectalis contraction.

Biofeedback and pelvic floor physical therapy are first-line for dyssynergic defecation.

Rectal prolapse: full-thickness prolapse in elderly patients often treated with perineal (Altemeier) or abdominal rectopexy; assess for concomitant incontinence.

Slow-transit constipation: confirmed with transit study (radiopaque markers or scintigraphy); surgery reserved for refractory, well-selected cases.

Pudendal neuralgia: pain relieved by sitting, worsened by sitting on hard surfaces; diagnosed by pudendal nerve block.

Colon injury: primary repair acceptable for most low-energy civilian injuries; diversion (colostomy) for destructive injuries, shock, or contamination.

Damage control laparotomy: temporary abdominal closure, correction of acidosis, hypothermia, and coagulopathy; planned re-exploration.

Splenic injury: nonoperative management for hemodynamically stable patients; embolization for active blush; splenectomy for instability.

Small bowel injury: repair or resection with primary anastomosis; avoid anastomosis in severe shock or peritonitis.

Diaphragmatic injury: left side more common with blunt trauma; laparoscopy or thoracoscopy for occult injury in penetrating thoracoabdominal wounds.

Mesenteric ischemia: SMA embolus classically at middle colic branch; CT angiography is diagnostic; laparotomy for infarction or peritonitis.

Acute appendicitis: laparoscopic appendectomy standard; antibiotics alone for uncomplicated cases in selected patients; interval appendectomy controversial.

Large bowel obstruction with competent ileocecal valve risks closed-loop perforation at cecum; cecal diameter >9-12 cm is a warning sign.

Enhanced recovery after surgery (ERAS): preoperative counseling, no routine mechanical bowel prep, carbohydrate loading, multimodal analgesia, early feeding, early ambulation.

VTE prophylaxis: low-molecular-weight heparin or unfractionated heparin for colorectal surgery; extend 4 weeks after cancer resection.

Surgical antibiotic prophylaxis: administer within 60 minutes before incision; redose for long cases or major blood loss.

Sepsis: recognize with SOFA/qSOFA; sepsis bundle includes cultures, broad-spectrum antibiotics within 1 hour, 30 mL/kg crystalloid for hypotension or lactate ≥4.

Acute respiratory distress syndrome: Berlin criteria - onset within 1 week, bilateral opacities, not cardiogenic, PaO2/FiO2 ≤300; low tidal volume ventilation 6 mL/kg.

Perioperative cardiac risk: revised cardiac risk index (RCRI) predicts major cardiac events; consider functional capacity and surgery-specific risk.

Ostomy care: stoma should be matured at initial surgery; high-output ileostomy (>1-1.5 L/day) risks dehydration and electrolyte loss.

Nutrition: early enteral feeding preferred; immunonutrition considered in malnourished patients undergoing major GI surgery.

Laparoscopic colectomy: oncologic equivalence to open surgery for colon cancer; conversion rates higher with obesity, adhesions, and locally advanced tumors.

Pneumoperitoneum: typically 12-15 mmHg CO2; physiologic effects include hypercapnia, decreased venous return, and increased airway pressures.

Robotic surgery advantages: articulating instruments, tremor filtration, three-dimensional visualization; useful in narrow pelvis for rectal cancer and prostate surgery.

Laparoscopic entry: open (Hasson) technique reduces major vascular and bowel injury versus closed Veress needle entry.

Single-incision and natural orifice approaches: cosmetic benefit but increased hernia risk and technical difficulty; not standard of care for all cases.

Intraoperative CO2 embolism: sudden hypotension, arrhythmia, and desaturation; treat by desufflation, 100% oxygen, left lateral decubitus position.

Enhanced recovery and ERAS protocols complement minimally invasive surgery, reducing length of stay.

Simulation-based training and credentialing are recommended before independent laparoscopic practice.

Informed consent: requires disclosure of diagnosis, proposed treatment, alternatives, and material risks; assess patient comprehension and voluntariness.

Belmont Report principles: respect for persons, beneficence, and justice; governs human subjects research.

Institutional review board (IRB) approval required before human subjects research; exempt and expedited categories exist.

Conflict of interest: disclose financial relationships with industry; manage and recuse when appropriate.

Levels of evidence: systematic reviews of RCTs highest; case reports and expert opinion lowest.

Sensitivity = true positives / (true positives + false negatives); specificity = true negatives / (true negatives + false positives).

Positive predictive value depends on disease prevalence; negative predictive value also varies with prevalence.

Professionalism: maintain competence, honesty in reporting, patient confidentiality (HIPAA), and appropriate boundaries.