Tropical infections and infestations in surgery

Overview

Tropical infections are common surgical problems in Pakistan and the region. Many are treated mainly with drugs, and the surgeon's role is to recognise complications (abscess rupture, obstruction, perforation) and to choose drainage, aspiration or operation at the right time.

This chapter covers amoebiasis, roundworm, hydatid disease, typhoid perforation, filariasis and mycetoma. Liver abscesses and hydatid of the liver are also discussed in the liver chapter.

Amoebiasis

Pathology

• Cause: Entamoeba histolytica, the commonest disease-causing amoeba in humans; most carriers have no symptoms.
• Faeco-oral spread of cysts in food or water (poor sanitation).
• Trophozoites invade the colon to form flask-shaped ("collar-stud") ulcers, mainly in the rectosigmoid and caecum.
• They reach the liver via the portal vein and cause liquefactive necrosis → abscess. Liver abscess is the commonest extra-intestinal complication.
• Right lobe ~80%, left ~10%, rest multiple; usually high on the diaphragmatic surface (hence chest complications). The right lobe is favoured possibly because superior mesenteric blood streams straight into it.
• Pus: chocolate-brown "anchovy sauce", odourless and sterile unless secondarily infected; trophozoites are found in the wall, rarely in the pus.

Clinical features

• Typically a young adult man: fever, sweats, weight loss, then right upper quadrant pain radiating to the right shoulder, hiccups, dry cough.
• Past bloody diarrhoea or a stay in an endemic region (often absent).
• Tender hepatomegaly, tender bulging intercostal spaces, pleural effusion, basal crackles; jaundice is uncommon.
• May rupture into the pleura (right), peritoneum or pericardium (left lobe).

Investigations

• Anaemia, leukocytosis, raised ESR/CRP, low albumin, raised alkaline phosphatase.
• Serology (IHA, ELISA): very sensitive outside endemic areas, but stays positive for a long time, so less useful in endemic areas.
• Ultrasound: hypoechoic lesion with ill-defined edge; used to guide aspiration. CT if doubtful (raised right hemidiaphragm, effusion).
• Sigmoidoscopy: ulcers; scrapings show trophozoites (differentiates from ulcerative colitis).

Treatment

• Medical treatment is first-line and very effective: metronidazole (or tinidazole), followed by diloxanide furoate for about 10 days to clear intestinal cysts.
• Aspiration (image-guided, may be repeated) if: large abscess, imminent rupture, left lobe (risk of pericardial rupture), no response to drugs after several days, or secondary infection.
• Surgery only for complications: rupture into pleura, peritoneum or pericardium (drain and lavage with drugs); toxic megacolon or severe haemorrhage (subtotal colectomy with ileostomy).

• Amoebiasis cutis: destructive, spreading skin ulceration around a drain or sinus site after drainage of an amoebic abscess; responds to metronidazole.

Amoeboma

• Chronic granulomatous mass, usually in the caecum, after incompletely treated infection.
• Right iliac fossa mass with bloody mucoid diarrhoea; may look like carcinoma on barium ("apple core") and colonoscopy.
• Biopsy is essential; a full drug course makes it regress (repeat colonoscopy after 3–4 weeks). Resect if it persists or cancer cannot be excluded.

Roundworm (Ascaris lumbricoides)

• Commonest intestinal nematode; faeco-oral; larvae pass through liver and lungs (Loeffler's syndrome: cough, eosinophilia), adults live in the small bowel (up to 45 cm long).
• Surgical complications: bolus obstruction of the terminal ileum in children, worms in the common bile duct (cholangitis, jaundice) or pancreatic duct (pancreatitis), rarely perforation, biliary stones.
• Diagnosis: eosinophilia, ova in stool; worms seen on plain film, barium (worms contain barium), ultrasound or MRCP of the bile duct.
• Treatment: obstruction is first treated conservatively (IV fluids, nasogastric suction, hypertonic saline enemas). Surgery if this fails or there is perforation: milk the bolus through the ileocaecal valve; enterotomy or resection only if needed. Ductal worms: ERCP extraction. Give a full anthelmintic course afterwards.

Hydatid disease

Parasite and life cycle

• Echinococcus granulosus (dog tapeworm).
• Dog = definitive host (adult worm in its gut). Sheep, cattle and humans = intermediate hosts (cysts).
• Humans swallow eggs from dog faeces (close contact with dogs; dogs fed raw offal). Common in sheep-rearing areas such as Balochistan.
• E. multilocularis (alveolar hydatid) invades like a tumour.

Cyst structure

Clinical features

• Liver most common (mostly right lobe), then lung; any organ (brain, spleen, kidney, bone).
• Often asymptomatic; otherwise a slowly enlarging painful RUQ mass.
• Complications: rupture into the biliary tree (colic, jaundice, cholangitis), into the peritoneum or bronchus (coughing up "grape skins"), secondary infection, and anaphylactic shock after rupture, even from minor trauma.

Diagnosis

• Eosinophilia; serology (ELISA, immunoelectrophoresis).
• Ultrasound and CT are investigations of choice: smooth cyst with septa/daughter cysts, a separated (floating) membrane, calcified wall in old cysts.
• WHO ultrasound groups: active (larger than 2 cm, often fertile), transitional, inactive (degenerated or calcified).
• Lung: meniscus (crescent) sign on X-ray (impending rupture); water-lily sign after rupture.
• Do not do a diagnostic needle aspiration outside a planned PAIR procedure (spillage and anaphylaxis).

Treatment

• Treat in a specialist unit (surgeon, physician, interventional radiologist).
• Inactive, asymptomatic, calcified cysts: observe with ultrasound.
• Albendazole before and after any procedure to reduce recurrence (praziquantel also used).
• PAIR (ultrasound-guided): Puncture, Aspiration, Injection of scolicidal agent, Re-aspiration.
• Surgery: pericystectomy (total or partial) with omentoplasty, de-roofing/marsupialisation (open or laparoscopic), or liver resection for peripheral cysts.
• Scolicidal agents: hypertonic saline (15–20%), ethanol, povidone-iodine; pack the field with soaked swabs to prevent spillage. If a scolicide enters a bile duct it can cause sclerosing cholangitis, so check for biliary communication first.
• Lung cysts: surgery preserving lung (cystotomy, capitonnage, segmentectomy).

Typhoid (enteric) perforation

Pathology

• Salmonella typhi, Gram-negative; faeco-oral spread.
• Infects Peyer's patches of the terminal ileum → hyperplasia, necrosis and longitudinal ulcers along the long axis of the bowel, on the antimesenteric side.
• Untreated or partly treated ulcers may bleed or perforate; perforation can be multiple and occasionally in the colon.

Diagnosis

• Fever for 2–3 weeks, toxic, distended (ileus), may have melaena.
• Sudden worsening with generalised abdominal pain in the 2nd–3rd week = perforation until proven otherwise. Signs of peritonitis may be masked in a very toxic patient.
• Erect chest X-ray (or lateral decubitus film): gas under the diaphragm.
• Blood (early) and stool cultures; Widal (O and H agglutinins) still used locally but unreliable; rapid IgM/IgG kits (Tubex, Typhidot).

Management

1. Resuscitate in high dependency/ICU; IV fluids, nasogastric tube, catheter.
2. IV antibiotics covering S. typhi, Gram-negatives and anaerobes (Bailey & Love lists cephalosporins, gentamicin and metronidazole).
3. Laparotomy soon after resuscitation:
   • Single perforation, good condition: freshen the edges and close in two layers (or wedge excision).
   • Multiple perforations or unhealthy bowel: resection and anastomosis, or ileostomy/exteriorisation in the very ill.
   • Always search for other perforations and necrotic patches about to perforate.
   • Thorough peritoneal lavage; close the sheath and leave the skin open (wound infection is almost certain); laparostomy in severe contamination.

• Prognosis is better if perforation happens early in the illness and the delay to surgery is short.

Lymphatic filariasis

• Wuchereria bancrofti (Brugia in about 10%), spread by mosquitoes; adult worms live in lymphatics and cause obstruction.
• Acute: recurrent fever, lymphangitis, lymphadenitis (filarial fever).
• Chronic: lymphoedema → elephantiasis of legs, scrotum and penis; hydrocele; chyluria (milky urine after fatty meals) and chylous ascites; tropical pulmonary eosinophilia (night cough, very high eosinophils).
• Secondary streptococcal cellulitis is common.
• Diagnosis: eosinophilia; sheathed microfilariae on a night (nocturnal) blood film; also in chylous urine, ascites or hydrocele fluid; antigen tests.
• Treatment: diethylcarbamazine (effective early, before gross elephantiasis), limb hygiene, elevation and compression (intermittent pneumatic compression). Hydrocele: excision and eversion of the sac. Debulking operations for elephantiasis are rarely successful.

Mycetoma (Madura foot)

Definition and cause

• Chronic, specific, granulomatous, progressive, destructive infection of skin, subcutaneous tissue and then fascia, muscle and bone.
• Eumycetoma = true fungi; actinomycetoma = bacteria (actinomycetes, e.g. Nocardia, Streptomyces).
• Organisms in soil enter through minor thorn pricks in barefoot workers; occurs in the "mycetoma belt" (Sudan, India and others). Not contagious.
• Foot in about 70%, hand about 12%.

Clinical features

• Triad: painless subcutaneous swelling, multiple sinuses, and discharge containing grains.
• Grains may be black, yellow, white or red depending on the organism (black usually fungal).
• Painless, so presentation is late; pain suggests secondary bacterial infection.
• Spreads along tissue planes; lymphatic spread commoner with actinomycetoma.

Diagnosis

• X-ray: soft tissue shadows, bone scalloping, periosteal reaction, punched-out cavities (can mimic osteosarcoma).
• Ultrasound separates eumycetoma (sharp bright grain echoes) from actinomycetoma.
• MRI: characteristic "dot-in-circle" sign (grains within granulomas).
• Deep biopsy (not under local anaesthesia) for histology and grain culture; FNAC; serology.

Treatment

• Wide excision under general or regional anaesthesia, debulking, or amputation for advanced disease. Recurrence after surgery is high; continue drugs after surgery.

Quick revision

• Amoebic abscess: right lobe, single, sterile anchovy pus; metronidazole then diloxanide; aspirate large, left lobe or impending rupture.
• Amoeboma: caecal mass mimicking cancer; biopsy and treat; resect if persistent.
• Roundworm obstruction: drip, suck, hypertonic saline enemas; milk into colon at surgery.
• Hydatid: dog is definitive host; endocyst is germinal; liver then lung; albendazole and PAIR; beware anaphylaxis.
• Lung hydatid: meniscus sign (about to rupture), water-lily sign (ruptured).
• Typhoid perforation: terminal ileum, antimesenteric, 2nd–3rd week; repair or exteriorise, search for others, skin left open.
• Filariasis: W. bancrofti, mosquito, night film, DEC; hydrocele and elephantiasis.
• Mycetoma: foot, painless, sinuses, grains; actinomycetoma drugs, eumycetoma azoles plus excision.

Written by The House Job from standard references (Bailey & Love's Short Practice of Surgery, 27th edition).

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