1. Case discussion ED conference 11/04/16
Jelte Kelchtermans

2. Case description:
A 5-year-old girl presents to the ED with a 4-day history of NBNB vomiting. The patient has had several episodes of watery non bloody diarrhea over the first two days of illness but has had well formed stools of the past two days. The patient also has a 5-day history of rhinorrhea.
Mother reports that over the last 24 hours the patient has been less active. No associated abdominal pain, dysuria, fever, chills, rash, cough, change in fluid intake or urine output.
The patient visited the ED on day 2 of illness and was diagnosed with a probable viral Gastroenteritis and discharged after passing an oral tolerance test. No significant past medical or surgical history. No significant family history. Not currently taking any medications. No known allergies. Vaccinations are up to date.
Bp 100/50 mmHg, RR 30/min, HR 140/min. The patients’ urine specific gravity is and her blood sodium level is 146 mmol/L.

3. What test is most likely to reveal the underlying diagnosis?
1. Brain MRI
2. Kidney MRI
3. ADH level
4. Water deprivation test
5. Stool culture

4. What test is most likely to reveal the underlying diagnosis?
1. Brain MRI
2. Kidney MRI
3. ADH level
4. Water deprivation test
5. Stool culture

5. Diabetes insipidus Polydipsia and polyuria:
Central Diabetes insipidus (most common with 3/100,000)
Nephrogenic diabetes insipidus
Compulsive water drinking

6. Central (Hypothalamic/Pituitary Lesions Leading to Insufficient Production or Release of ADH)
Postoperative brain surgery
Intracranial lesions (cysts, aneurysms, tumors of pituitary, brainstem)
Infiltrative malignancies (lymphoma, leukemia)
Infections, including encephalitis, meningitis, abscess
Head trauma
Hypoxic injury
Congenital, inherited as an autosomal dominant disorder

7. Nephrogenic (Resistance to ADH due to interference with the Renal Concentrating Mechanism)
Acquired metabolic aberrations
Hypokalemia (chronic, Bartter syndrome)
Hypercalcemia
Hypercalciuria (rare)
Diabetes mellitus
Medullary damage
Chronic pyelonephritis
Infiltrative disease (leukemia, lymphoma, amyloidosis)
Sickle cell disease
Cystinosis
Other forms of chronic renal failure
Obstructive uropathy
Drugs (lithium, demeclocycline, amphotericin B, diphenylhydantoin)
Inherited
X-linked
Autosomal recessive
Autosomal dominant

8. Pathophysiology

9. Presentation
Poor feeding + failure to thrive due to excessive fluid consumption and blunted appetite
Irritability due to hypernatremia and dehydration
Nocturia due to large urine volume
Constipation due to dehydration
Seizures and dehydration may develop with late recognition of the disease
High urine output despite dehydration

10. Diagnosis Blood/urine glucose (DD DM) 24 hour urine
Urinary specific gravity
Water deprivation test (DD severe DI vs mild DI and polydipsia)
DDAVP intranasal test (DD Nephrogenic and Central DI)
MRI of the brain (Loss of bright T1-weighted signal within the sella)

11. Management Sufficient water to maintain normal electrolytes
Low renal solute load to minimize water loss
If urine concentrates to 1,000 mOsm/kg of water (normal), the kidney can excrete a solute load of 300 mOsm in 300 mL of urine. However, if urine concentrates only to 100 mOsm/kg of water, excreting 300 mOsm requires 3 L of urine.
Adequate calories to support growth. Pharmacotherapy (E.g Thiazide, NSAID) usually is needed.

12. References
Diabetes Insipidus. Pablo Saborio, Gary A. Tipton, James C.M. Chan. Pediatrics in Review Apr 2000, 21 (4)  ; DOI:  /pir
Back to Basics. Michael A. Linshaw. Pediatrics in Review Oct 2007, 28 (10)  ; DOI:  /pir
Central diabetes insipidus misdiagnosed as acute gastroenteritis in a pediatric patient. Laleh Gharahbaghian, MD et all. Canadian Journal of Emergency Medicine, 10(5), pp. 488–492. doi: /S