title: "Week 4: Gastroenterology, Ophthalmology & Renal"
Week 4: Gastroenterology, Ophthalmology & Renal
1. Gastroenterology
Diarrhoea and Malabsorption
Malabsorption presents as diarrhoea - may be fatty (steatorrhoea), watery, or bloody.
Steatorrhoea
Fat absorption requires:
- Gastric acid (hydrolysis)
- Bile salts (solubilise fat)
- Pancreatic enzymes (digest fat)
- Intact intestinal mucosa (absorption)
Short-chain triglycerides can enter portal venous system directly (bypass lymphatics) - excellent supplement for malabsorption.
Stool Assessment:
| Finding | Implies | Investigation |
|---|---|---|
| Fat globules | Lipase deficiency or liver disease | Faecal elastase, CF sweat test |
| Fatty acid crystals | OK digestion but poor uptake | Small bowel biopsy |
Suspect cystic fibrosis in a child with meconium ileus, chronic steatorrhoea, FTT, and respiratory illness!
Watery Diarrhoea
Osmotic diarrhoea stops on fasting; secretory diarrhoea persists on fasting.
Stool osmotic gap: 280 - 2 x (Stool Na + Stool K)
- Normal: 50-100
- >100 = osmotic diarrhoea
- Disaccharidase deficiency (lactase, sucrase)
- Glucose-galactose malabsorption
- Excessive sorbitol/fructose intake
Clinical features of osmotic diarrhoea: stops when feeds stop, mild hyperchloraemic acidosis, stool acidity causing perianal excoriation.
Monosaccharide malabsorption is life-threatening - causes massive fluid loss. Treatment: remove the offending carbohydrate.
Bloody Diarrhoea
Causes:
- Infection: Bacterial, parasitic
- IBD: Crohn's, UC, milk protein intolerance
Blood is not always obvious in stool - must do microscopy. RBCs and leukocytes suggest colitis.
Coeliac Disease
Immune-mediated inflammatory disease of small intestine caused by gluten sensitivity in genetically predisposed individuals. 1 in 100 prevalence.
Genetics: HLA DR3-DQ2 (90%) or HLA DR4-DQ8 (10%)
Presentation:
- GI (Gastrointestinal): Diarrhoea/steatorrhoea or constipation, FTT, abdominal distension
- Extra-intestinal: Iron-deficiency anaemia, fatigue, dental defects, dermatitis herpetiformis, short stature
- Iron deficiency anaemia (unexplained or Fe-resistant)
- IgA deficiency
- Down Syndrome, Turner Syndrome, Williams Syndrome
- First-degree relatives with coeliac disease
Diagnosis:
- Made on gluten-containing diet (3g gluten/day)
- If on GFD, challenge with 10g/day for 8 weeks then re-test
Coeliac serology: Anti-tissue transglutaminase IgA (first-line, most sensitive). If low anti-TTG but high suspicion, suspect IgA deficiency and order DGP-IgG.
ESPGHAN 2020 Criteria (no biopsy needed):
- Normal IgA + anti-TTG IgA >10x ULN
- AND positive endomysial antibody (EMA) on separate sample
Treatment: Lifelong GFD
Inflammatory Bowel Disease (IBD)
Crohn's Disease
Crohn's disease affects mouth to anus. Small bowel Crohn's may present insidiously with non-specific abdominal pain, loose stool, and growth failure.
Diagnosis:
- Faecal calprotectin (best in >2 years old)
- Gold standard: Endoscopy and biopsy showing chronic inflammation +/- granulomas
Complications: Fistulas, stenosis, bowel obstruction, malabsorption
Acute Severe Colitis
1-2% with acute severe colitis develop toxic megacolon: colonic dilatation ≥56mm, fever, tachycardia, dehydration.
Source: Local paediatric gastroenterology guideline.
Jaundice in Children
Conjugated hyperbilirubinaemia = conjugated fraction ≥20% total. In a neonate, conjugated jaundice is always abnormal.
Source: Local neonatal jaundice/cholestasis guideline.
The most important question to ask: stool colour. Acholic (pale) stool = failure of bile to enter intestine.
Biliary Atresia
Biliary atresia is the leading cause of cholestatic jaundice in paediatrics and top indication for paediatric liver transplant in Australia.
Presentation: 2-6 weeks of life with conjugated hyperbilirubinaemia, dark urine, progressively pale stools
Management: Kasai portoenterostomy - connect small intestine to porta hepatis
- The earlier the better (<60 days old)
- 1/3 good drainage
- 1/3 good then fail (need transplant)
- 1/3 fail immediately
2. Ophthalmology
Conjunctivitis in Children
| Feature | Bacterial | Viral | Allergic |
|---|---|---|---|
| Organism | H. influenzae, S. pneumoniae, S. aureus | Adenovirus | - |
| Season | Autumn/Winter | Summer | Spring |
| Laterality | Usually unilateral | Usually bilateral | Bilateral |
| Itching | None | Limited | Primary complaint |
| Discharge | Mucopurulent | Watery with mucus | Watery |
| Treatment | Topical chloramphenicol | Self-limiting, lubricants | Antihistamines, Patanol |
A good rule of thumb: topical steroids are not prescribed for children with conjunctivitis.
Neonatal Conjunctivitis
Pathogen by onset day:
- Day 0-2: Chemical (irritant/prophylaxis)
- Day 2-5: Gonococcal
- Day 5-14: Chlamydia
- Day 6-14: Herpes simplex
- Other bacterial: variable (often 4-7 days)
For chlamydial conjunctivitis: treat with oral erythromycin 50 mg/kg/day (systemic therapy). Remember to treat the parents!
Source: eTG; local paediatric ophthalmology guideline.
HSV Conjunctivitis
Presentation: Red, swollen eyelid with vesicles, watery discharge
Always examine cornea for dendritic ulcer. Never use steroids - can cause viral particles to enter corneal stroma leading to scarring and vision loss.
Strabismus
Strabismus (misalignment of eyes) affects 2% of children. Risk factors: FHx, prematurity, refractive error, neurological disorder.
Source: Local paediatric ophthalmology teaching.
Pseudostrabismus: Children with broad flat noses and epicanthal folds may appear to have strabismus but don't. Assess symmetry of corneal reflections.
| Type | Onset | Features | Treatment |
|---|---|---|---|
| Infantile esotropia | First few months | Constant, cross-fixation | Surgery within 12 months |
| Accommodative esotropia | 2-3 years | Intermittent, associated with hyperopia | Glasses first |
| Intermittent exotropia | <5 years | Eye drifts outward, worse with fatigue | Non-surgical first |
Amblyopia
Amblyopia = reduced vision in one eye due to abnormal visual development. Affects 2% of children (same as strabismus).
Source: Local paediatric ophthalmology teaching.
Causes:
- Strabismus (most common)
- Anisometropia (different refractive error each eye)
- Deprivation (ptosis, cataract)
Critical period for treatment is before age 7-8. After this, visual pathways are less plastic.
Leukocoria (White Pupil)
Red flag: Always investigate leukocoria. Differential includes retinoblastoma, congenital cataract, retinal detachment.
3. Renal
Urinary Tract Infection (UTI (Urinary Tract Infection))
UTI (Urinary Tract Infection) is extremely common - 5% of febrile children have a UTI (Urinary Tract Infection). Male > Female until 12 months, then Female > Male.
Source: Local paediatric UTI guideline.
Commonest pathogen: >80% E. coli
30% have vesico-ureteric reflux. Beware a urinary tract anomaly in a child with Pseudomonas UTI (Urinary Tract Infection).
Source: Local paediatric UTI guideline; paediatric urology teaching.
| Infants | Children |
|---|---|
| Poor feeding, vaguely unwell | Dysuria, frequency |
| Fever of unknown origin | Abdominal/loin pain |
| Neonatal jaundice | Incontinence |
| Vomiting | Haematuria (think Proteus) |
Diagnosis:
- Preverbal/not toilet-trained: In-out catheter
- Verbal/toilet-trained: Clean catch specimen
- Dipstick: Both leukocytes AND nitrites positive = ≥97% chance of UTI (Urinary Tract Infection)
Treatment:
| Clinical | Antibiotics | Route | Duration |
|---|---|---|---|
| Afebrile (cystitis) | Cephalexin/Bactrim | Oral (Per Os (by mouth)) | 3 days |
| Febrile (pyelonephritis) | Cephalexin/Bactrim | Oral (Per Os (by mouth)) | 7 days |
| <1 month or very unwell | Ampicillin + Gentamicin | IV (Intravenous) | 48h afebrile then 7 days oral |
Nephrotic Syndrome
Triad: Proteinuria, hypoalbuminaemia, and oedema. May also have hypercholesterolaemia.
- 80% present under 6 years old
- 80% have minimal change disease
- 80% are steroid responsive
- 80% relapse
Diagnosis:
- Heavy proteinuria (dipstick >3+ or spot PCR >200 mg/mmol)
- Hypoalbuminaemia (<25 g/L)
- Oedema
Complications: Hypovolaemia, severe oedema, infection/sepsis (urinary loss of Ig), coagulopathy, severe hypertension. Pneumococcus can cause spontaneous bacterial peritonitis (SBP (Systolic Blood Pressure)).
Red Flags (not minimal change disease):
- Renal impairment, significant HTN (Hypertension)
- Age <1 year or >10-12 years
- Macroscopic haematuria, RBC casts
- Steroid-resistant
Treatment:
- First episode: Oral prednisolone 60 mg/m2 for 4-6 weeks then wean
- No added salt diet
- Pneumococcal + annual flu vaccine
Nephritic Syndrome
Classic features: Haematuria (may be cola-coloured), hypertension, mild-moderate proteinuria.
Post-Streptococcal Glomerulonephritis (PSGN)
PSGN: Self-limiting condition 2-4 weeks after GAS pharyngitis or impetigo. Triad of hypertension, haematuria, and oedema.
- Greater incidence in Aboriginal and Torres Strait Islander peoples
- C3 is low (alternative complement pathway activation)
- C4 usually normal
Management: Mostly supportive - fluid management, furosemide if overloaded, antibiotics if active strep infection
Course: Macroscopic haematuria resolves in 1-2 weeks, proteinuria in 6 weeks, microscopic haematuria may persist 2 years, low complement normalises in 5-8 weeks.
- Rashes + swollen joints = lupus or IgA vasculitis (HSP)
- Low C3/C4 = SLE
- Previous haematuria + hearing loss = Alport syndrome
- Rapidly rising creatinine = RPGN
Hypertension in Childhood
Hypertension: SBP (Systolic Blood Pressure) or DBP (Diastolic Blood Pressure) >95th centile by age and height. Cuff bladder should be >40% of mid-upper arm width.
Primary (essential): Most common in children >6 years, associated with obesity/family history
Secondary: More common in children <6 years, renal disease most prevalent cause
| Age | Common Causes |
|---|---|
| Infants | Renal vein/artery thrombosis, coarctation, congenital renal abnormalities |
| Young children | Tumours (Wilms, neuroblastoma), renal disease, vascular |
| Older children | Renal disease, renovascular, endocrine, essential HTN (Hypertension) |
| Adolescents | Essential HTN (Hypertension), renal disease |
4. Gastroenteritis
Acute gastroenteritis is the most common cause of vomiting and diarrhoea in children. Rotavirus was the leading cause before vaccination; now norovirus predominates. Bacterial causes include Salmonella, Campylobacter, Shigella, and enterotoxigenic E. coli.
Assessment of Dehydration
| Feature | Mild (3-5%) | Moderate (5-10%) | Severe (>10%) |
|---|---|---|---|
| Mucous membranes | Slightly dry | Dry | Parched |
| Eyes | Normal | Sunken | Deeply sunken |
| Fontanelle (if open) | Normal | Sunken | Sunken |
| Skin turgor | Normal | Decreased | Tenting |
| Peripheral perfusion | Normal | Prolonged CRT | Mottled, cool |
| Urine output | Decreased | Oliguria | Anuria |
| Mental state | Alert | Irritable/lethargic | Obtunded |
Red flags in gastroenteritis:
- Bilious (green) vomiting = surgical cause until proven otherwise (malrotation/volvulus)
- Bloody diarrhoea with fever = consider HUS (E. coli O157:H7), intussusception, or IBD
- Persistent vomiting without diarrhoea = consider non-GI causes (raised ICP, DKA, UTI)
Management
Oral rehydration is first-line for mild-moderate dehydration. Use oral rehydration solution (ORS) at 10 mL/kg for each loose stool. If unable to tolerate oral fluids, use nasogastric rehydration before IV fluids.
Source: Local paediatric gastroenteritis guideline (e.g., RCH CPG).
Ondansetron (single oral dose) reduces vomiting and the need for IV fluids in moderate gastroenteritis. However, it is not routinely recommended for mild cases.
- IV fluids: 0.9% saline 10-20 mL/kg boluses for severe dehydration or shock
- Antibiotics: NOT routine. Only for bloody diarrhoea with systemic toxicity, immunocompromised, or neonates
- Anti-diarrhoeals (loperamide): Contraindicated in young children
Practice Questions
What is the most appropriate initial management?
What is the most appropriate first-line investigation?
What is the most likely underlying histological diagnosis?
What is the most likely causative organism?