Postoperative Complications

Postoperative complications are events that deviate from the expected recovery course after surgery. NEET PG loves this topic because it tests timing-based reasoning ("fever on POD-2 vs POD-7"), drug-of-choice, and the surgeon's next step. Master the clock — most answers hinge on the postoperative day (POD) at which a problem appears.

Classification by timing

Complications are best organised by when they appear after surgery, because the timeline itself is the single biggest examiner clue.

Time frame	Typical complications
Immediate (0–24 h)	Reactionary haemorrhage, primary haemorrhage, airway obstruction, hypotension, malignant hyperthermia
Early (1–7 days)	Atelectasis, pneumonia, UTI, wound infection (early), paralytic ileus, anastomotic leak, DVT, urinary retention
Late (after 1 week)	Secondary haemorrhage, wound dehiscence/burst abdomen, incisional hernia, adhesive obstruction, fistula, keloid

High-yield: The classic "ladder of postoperative fever" = the 5 W's — Wind (atelectasis, POD 1–2), Water (UTI, POD 3–5), Wound (infection, POD 5–7), Walking (DVT/PE, POD 5+), Wonder drugs / What-did-we-do (drug fever, line sepsis, transfusion — any time).

Postoperative haemorrhage

Bleeding after surgery is classified by timing, and each type has a distinct mechanism and management — a perennial one-liner question.

Type	Timing	Cause	Management
Primary	During surgery	Direct vessel injury at operation	Intra-op haemostasis
Reactionary	Within 24 h (usually 4–6 h)	Slipped ligature, dislodged clot, rise in BP, reopening of vessels in spasm, coughing/straining	Re-exploration and haemostasis
Secondary	7–14 days (usually POD 7–10)	Infection eroding a vessel or sloughing	Treat sepsis; ligation/embolisation; proximal control

High-yield: Reactionary haemorrhage is most often due to a slipped ligature or dislodgement of clot as blood pressure normalises after the hypotension of anaesthesia. Secondary haemorrhage is almost always due to infection.

Clinical recognition flow: Tachycardia → narrowing pulse pressure → falling urine output → hypotension (a late sign) → suspect concealed haemorrhage. Young patients compensate well and crash late; do not be reassured by a "normal" BP.

Pulmonary complications: atelectasis & pneumonia

Atelectasis is the commonest cause of fever in the first 48 hours and the commonest postoperative pulmonary complication overall. Collapse of distal alveoli follows shallow breathing (pain), retained secretions, and reduced surfactant.

• Risk factors: smoking, COPD, obesity, upper-abdominal/thoracic incisions, prolonged anaesthesia.
• Features: low-grade fever POD 1–2, tachypnoea, reduced breath sounds at bases, mild hypoxia.
• Investigation: chest X-ray (patchy collapse, raised hemidiaphragm); pulse oximetry.
• Management: chest physiotherapy, incentive spirometry, early mobilisation, adequate analgesia, deep breathing — prevention is the cure. Untreated atelectasis → consolidation/pneumonia by POD 3–5.

High-yield: Fever on POD 1–2 with basal crepitations and a clear-ish chest film = atelectasis. Treat with physiotherapy and spirometry, NOT antibiotics first.

Wound dehiscence and burst abdomen

Wound dehiscence = partial or complete separation of the layers of a surgical wound. Burst abdomen = complete dehiscence of an abdominal wound with protrusion of viscera (evisceration), classically presenting on POD 6–8.

Pathognomonic sign: sudden discharge of serosanguinous ("salmon-pink/blood-stained serous") fluid from the wound — this precedes frank burst abdomen and is a warning to act.

Causes (split into general and local):

General (patient)	Local (technique/wound)
Old age, malnutrition, hypoproteinaemia	Poor surgical technique / suturing
Diabetes, obesity	Wound infection (commonest local cause)
Malignancy, jaundice, uraemia	Inadequate suture material / knot slip
Steroids, chemotherapy, smoking	Raised intra-abdominal pressure (cough, ileus, ascites, straining)
Vitamin C / zinc deficiency	Haematoma, poor tissue apposition

Immediate management of burst abdomen → 1. Reassure, lie patient flat. 2. Cover protruding bowel with sterile saline-soaked gauze. 3. Analgesia, IV fluids, broad-spectrum antibiotics, nasogastric tube. 4. Take back to theatre for resuturing using mass closure / deep tension sutures.

High-yield: Salmon-pink serosanguinous discharge on POD ~7 = impending burst abdomen. Prevention = Jenkins' rule (suture length : wound length ≥ 4:1) with mass closure.

High-yield: Incisional hernia is the late sequel of a healed dehiscence/wound infection; burst abdomen is the acute event.

Anastomotic leak

Leakage of luminal contents from a surgical join — the most feared GI complication, classically presenting POD 5–7 (range 3–10).

• Risk factors (anastomosis fails when): poor blood supply, tension on the anastomosis, sepsis/contamination, hypoalbuminaemia, steroids, radiation, ischaemia, diabetes, low rectal/oesophageal site (highest leak rates), emergency surgery.
• Features: spiking fever, tachycardia, abdominal pain, ileus that fails to resolve, faeculent/bilious discharge from drain, peritonism, raised CRP. Tachycardia and a "failure to thrive"/not progressing as expected are early subtle clues.
• Investigation of choice: CT abdomen with oral/rectal water-soluble contrast (Gastrografin) — shows leak, collection, free gas/fluid. Water-soluble contrast study confirms a leak; avoid barium (mediastinitis/peritonitis risk).
• Management: depends on the patient and leak size.
  • Stable, contained leak → conservative: NPO, IV antibiotics, IV fluids, drainage of collection (percutaneous), nutritional support.
  • Unstable / generalised peritonitis / free leak → re-laparotomy, washout, defunctioning stoma (exteriorise or proximal diversion), drainage.

High-yield: Persistent tachycardia is the earliest sign of an anastomotic leak — "the leak is tachycardia until proven otherwise." Investigate before waiting for peritonitis.

DVT and pulmonary embolism

Venous thromboembolism reflects Virchow's triad — stasis (immobility, surgery), endothelial injury (pelvic/orthopaedic surgery), hypercoagulability (malignancy, OCP, surgery itself). Calf-vein DVT typically appears POD 5–10.

• Risk factors: age >40, obesity, malignancy, prolonged surgery, pelvic/hip/knee surgery, previous VTE, OCP/HRT, immobility.
• Features: unilateral calf swelling, pain, warmth, tenderness; Homans' sign (calf pain on dorsiflexion — unreliable). PE → sudden dyspnoea, pleuritic chest pain, tachycardia, hypoxia, collapse.
• Investigation of choice: Compression duplex ultrasound for DVT; CT pulmonary angiography (CTPA) for PE. D-dimer has high negative predictive value — useful to rule out in low-probability cases. Wells score guides pre-test probability.
• Management: low-molecular-weight heparin (e.g., enoxaparin) → bridge to oral anticoagulation (warfarin or a DOAC) for ≥3 months; massive PE with shock → thrombolysis. Prophylaxis is examined heavily: early mobilisation, graduated compression stockings + intermittent pneumatic compression + LMWH (mechanical + pharmacological).

High-yield: Mnemonic — "THROMBOSIS" prophylaxis trio: mechanical (TED stockings/IPC) + chemical (LMWH) + early ambulation. In patients with active bleeding risk, use mechanical methods alone.

Paralytic ileus vs mechanical obstruction

A frequent exam discriminator. Some degree of physiological ileus is normal after laparotomy (small bowel recovers ~24 h, stomach ~24–48 h, colon last, ~48–72 h). It becomes pathological if it persists beyond ~3–5 days.

Feature	Paralytic ileus	Mechanical (early adhesive) obstruction
Onset	Usually continuous from surgery, POD 0–3	Often after an initial return of function, POD 5+
Bowel sounds	Absent / silent abdomen	Exaggerated, high-pitched, "tinkling"
Pain	Diffuse discomfort, painless distension	Colicky pain
Vomiting	Effortless, gradual	Prominent, may be bilious/faeculent
Distension	Generalised	Variable, depends on level
AXR / CT	Gas throughout including colon & rectum	Dilated loops with air–fluid levels, collapsed distal bowel, transition point
Treatment	Conservative — correct cause	Conservative trial → surgery if no resolution/strangulation

• Causes of prolonged ileus: electrolyte disturbance (hypokalaemia, hyponatraemia, hypomagnesaemia), opioids, intra-abdominal sepsis/leak, retroperitoneal haematoma, immobility, anticholinergics.
• Management of ileus → "drip and suck": NPO, NG tube decompression, IV fluids, correct electrolytes (especially potassium), stop/minimise opioids, treat sepsis, mobilise. Prokinetics have limited evidence; chewing gum and early enteral feeding aid recovery.

High-yield: A silent, soft, distended abdomen = ileus; colicky pain with tinkling bowel sounds and air–fluid levels = mechanical obstruction. Always check and correct hypokalaemia in postoperative ileus.

Postoperative urinary retention

Inability to void despite a full bladder — among the commonest early postoperative problems, especially after pelvic, anorectal, hernia, and spinal/epidural anaesthesia.

• Causes: pain, recumbency, anaesthetic and opioid effects, anticholinergics, BPH, overfilling, neurogenic (spinal anaesthesia).
• Features: suprapubic discomfort/fullness, inability to pass urine, palpable bladder, overflow incontinence; bladder scan confirms residual volume.
• Management → 1. Privacy, ambulation, warm tap, analgesia, run a tap. 2. If failed and volume large → urethral catheterisation (in-and-out or indwelling). 3. Treat reversible causes; consider alpha-blocker (tamsulosin) in BPH.

High-yield: Retention is the most common reason for catheterisation after hernia and haemorrhoid surgery; spinal anaesthesia is a classic precipitant.

Postoperative sepsis & SIRS

Surgical sepsis usually arises from wound infection, anastomotic leak, intra-abdominal collection/abscess, pneumonia, UTI, or line infection. Recognise it via SIRS criteria and act on the "Sepsis Six" bundle.

SIRS (≥2 of): temperature >38°C or <36°C; HR >90; RR >20 (or PaCO₂ <32); WBC >12,000 or <4,000 or >10% bands.

Sepsis Six (within 1 hour) → Give 3, Take 3:

1. Give high-flow oxygen.
2. Give IV broad-spectrum antibiotics (after cultures).
3. Give IV fluid resuscitation.
4. Take blood cultures (and source samples).
5. Take lactate (and haemoglobin).
6. Take/monitor urine output (catheterise).

High-yield: Source control (drainage of pus, removal of infected line, repair of leak) is essential — antibiotics alone will not cure an undrained abscess. A collection on POD 5–7 with swinging pyrexia = abscess → drain it (often percutaneous CT/US-guided).

Other named complications worth knowing

• Wound infection (surgical site infection): POD 5–7; Staphylococcus aureus most common in clean wounds; managed by opening the wound, drainage, dressings ± antibiotics. Risk graded by wound class — clean (<2%), clean-contaminated, contaminated, dirty (>10%).
• Seroma/haematoma: fluid/blood collection under wound; aseptic aspiration or evacuation.
• Fistula: abnormal communication; remember "FRIEND" factors that prevent closure — Foreign body, Radiation, Infection/IBD, Epithelialisation, Neoplasm, Distal obstruction. High-output enterocutaneous fistula → fluid/electrolyte loss, skin excoriation; manage with SNAP (Sepsis control, Nutrition, define Anatomy, Procedure/plan).
• Pressure sores, decubitus ulcers: in immobile patients — prevent with turning and pressure relief.
• Malignant hyperthermia: rare anaesthetic emergency (suxamethonium/halothane) → masseter spasm, rising end-tidal CO₂, hyperthermia; treat with dantrolene.

Recently asked / exam angle

• Timing matchers are the favourite format: "Fever on POD 2 → atelectasis"; "POD 5 → UTI"; "POD 7 with salmon-pink discharge → burst abdomen"; "POD 7–10 bleed → secondary haemorrhage (infection)."
• Reactionary vs secondary haemorrhage cause (slipped ligature/clot vs infection) and management (re-explore vs treat sepsis) is a near-guaranteed one-liner.
• Investigation of choice questions: anastomotic leak → CT with water-soluble oral/rectal contrast; DVT → compression duplex US; PE → CTPA.
• Earliest sign of anastomotic leak = persistent tachycardia.
• Jenkins' rule (4:1) and mass closure for preventing burst abdomen.
• Ileus vs obstruction table (silent vs tinkling, gas pattern, colic) and hypokalaemia as a correctable cause of ileus.
• VTE prophylaxis components (mechanical + LMWH + mobilisation) and contraindication to chemical prophylaxis in active bleeding.
• Sepsis Six / SIRS criteria and the principle of source control.
• FRIEND mnemonic for non-healing fistula and dantrolene for malignant hyperthermia appear as standalone facts.

Rapid revision

1. Commonest cause of fever in first 48 h = atelectasis; treat with physiotherapy and incentive spirometry, not antibiotics.
2. Reactionary haemorrhage (<24 h) = slipped ligature/dislodged clot → re-explore; secondary haemorrhage (POD 7–14) = infection eroding vessel.
3. Burst abdomen = POD ~7, heralded by salmon-pink serosanguinous discharge; cover with saline gauze + resuture.
4. Jenkins' rule: suture-to-wound length ratio ≥ 4:1 with mass closure prevents dehiscence.
5. Anastomotic leak = POD 5–7; persistent tachycardia is the earliest sign; confirm with water-soluble contrast CT.
6. Free/uncontained leak with peritonitis → re-laparotomy + defunctioning stoma; contained stable leak → conservative + percutaneous drainage.
7. Paralytic ileus = silent abdomen, gas throughout colon; mechanical obstruction = colicky pain, tinkling sounds, air–fluid levels.
8. Always correct hypokalaemia in prolonged postoperative ileus; manage with NG decompression + IV fluids ("drip and suck").
9. DVT POD 5–10 — duplex US is investigation of choice; PE → CTPA; D-dimer rules out, not in.
10. VTE prophylaxis = mechanical (stockings/IPC) + LMWH + early mobilisation; mechanical alone if active bleeding.
11. Urinary retention is commonest after hernia/anorectal surgery and spinal anaesthesia → catheterise if conservative measures fail.
12. Source control beats antibiotics alone in surgical sepsis; FRIEND factors keep a fistula open; dantrolene treats malignant hyperthermia.