The above is a comprehensive, textbook-referenced discussion. Here is a concise orientation to help navigate the full response:

Introduction: CDH arises from incomplete fusion of the pleuroperitoneal folds by 9 weeks of gestation, creating a posterior Bochdalek defect (70-75%, left-sided 85%), anterior Morgagni defect (23-28%), or central defect. Incidence is 1:2000-5000 live births. The primary pathophysiology is bilateral pulmonary hypoplasia and a reactive, hypoplastic pulmonary vasculature causing pulmonary hypertension - not simply the mass effect of herniated bowel.

Diagnosis: Prenatal ultrasound confirms from 15 weeks onward; postnatal chest X-ray showing bowel loops in the hemithorax, mediastinal shift, and scaphoid abdomen is classic. Lung-to-head ratio (LHR) is the key prognostic sonographic marker.

Treatment: The modern approach is preoperative stabilization first, not immediate surgery. Key pillars are: permissive hypercapnia ventilation (PIP <25-30 cmH2O, PaCO2 45-65 mmHg, SpO2 >85%), HFOV, inhaled nitric oxide, sildenafil, milrinone, ECMO for severe cases, and then delayed surgical repair at 48-72 hours via subcostal approach with patch repair for large defects. FETO (fetal tracheal occlusion balloon) at 27-29 weeks improves outcomes in severe cases.

Anaesthetic Management: Avoid bag-mask ventilation and N2O entirely. Intubate without neuromuscular blockade or with RSI. Maintain low PIP, permissive hypercapnia, preductal SpO2 monitoring, and treat any sudden desaturation as contralateral pneumothorax until proven otherwise. Do NOT forcibly expand the ipsilateral hypoplastic lung. Continue pulmonary vasodilators perioperatively.

Introduction: ARM results from failure of the urorectal septum to descend and divide the cloaca by week 6 of gestation. Incidence is 1:2500-5000 live births. ARM ranges from low cutaneous/vestibular fistulas to high lesions (rectourethral/rectovesical fistula) to cloacal malformations. AVF (anovestibular fistula) is the most common ARM in females - a low lesion with the rectum opening into the vaginal vestibule - and carries a favorable prognosis for continence.

Diagnosis: Perineal inspection is the first and most important step. Low lesions are visible as fistulas; high lesions show flat gluteals, absent sphincter reflex, and eventually bowel obstruction. Investigations include perineal ultrasound (replaces the invertogram), distal colostogram, MRI for sacral/spinal anatomy, and full VACTERL workup (echo, renal USS, spinal X-ray).

Treatment: Low lesions (including AVF) can undergo primary perineal anoplasty/PSARP without a colostomy. High lesions require a three-stage approach: neonatal sigmoid colostomy, then PSARP at 1-3 months (prone position, posterior sagittal incision), then colostomy closure at 6-8 weeks post-PSARP. Cloaca requires complex multi-structure reconstruction.

Anaesthetic Management: Treat every case as a full stomach (RSI mandatory). Correct fluid/electrolyte deficits preoperatively (target Na ≥130, UO 1-2 mL/kg/hr). Avoid N2O. Use ketamine/etomidate in hemodynamically unstable patients. Regional analgesia (caudal block for perineal surgery; epidural for complex cases) is highly effective but sacral anatomy must be checked first given association with sacral agenesis. PSARP is performed prone - airway must be doubly secured before turning. Monitor glucose (hypoglycemia risk in neonates) and temperature aggressively.