Diagnosis of Hypokalemia

Mahmoud Barazi, M.D.Nephrology Fellow

TTUHSC

Case

• 77 y.o WF who presented with a chief complain of Diarrhea.

• Also found to have Hypokalemia and Hypomagnesaemia.

• HPI:- 7 days hx of diarrhea with decreased oral intake.- No F/C/S

Case

• PMH- Non-Hodgkin’s lyphoma S/P Autologus BMT- HTN- AKD- CHF

Case

• Home Medications:- ASA 81 mg daily- Lasix 20 mg daily- Robitussin 20 mEq p.o BID- Tylenol 650 mg PO q4h prn- Folic Acid 1 mg po bid- Loratadine 10 mg po daily

Physical Exam

• VS: Tmp 99 HR 94 BP 101/51 RR 16 SaO2 92%Gen: A&O x 3, in mild distressHEENT: AT/NC, EOMI, PERRLANeck: Supple, No JVD, No thyromegalyChest: CTABCVS: S1, S2 normal, No M/R/G, NSRABD: Soft, NT, BS present, No organomegalyEXT: No C/C/E

Labs @ presentation

• WBC 6.2 Hgb 11.3 Plt 60• Na 137 K 2.1 Cl 95 CO2 28

AG 16 Glu 101 BUN 18 Cr 1.1Ca 7.8 Alb 3.2 Mg 1.4

• UA pH 6.5 Trace Protein Positive NitriteModerated Leuk. Esterase Spec Gravity 1.009

Cloudy RBC 0-3 WBC 15-2• C-Diff neg. Urine culture was positive for E.coli

Causes of Hypokalemia

• Decreased K Intake• Increased entry into cells

- Elevation in pH- Increased Insulin- Elevated B-agonist activity- Hypokalemic periodic paralysis- Marked increase in blood cell production- Hypothermia- Chlorquine intoxication

Causes of Hypokalemia

• Increased GI losses- Vomiting- Diarrhea- Tube drainage- Laxative abuse

Causes of Hypokalemia• Increased urinary losses

- Diuretics- Primary mineralocorticoid excess- Loss of gastric secretions- Nonreabsorable anions- Metabolic acidosis- Hypomagnesaemia- Amphotericin B- Salt-wasting nephropathies – including Batter’s or Gitelman’s syndrome- Polyuria

Diagnosis of Hypokalemia

• Can usually be determined from the history• In other case, the diagnosis is not readily

apparent• Measurement of BP, urinary K exertion and

assessment of AB balance are often helpful

Urinary Response

Urinary Response

Urinary response

• The minimum urine K concentration in response to Hypokalemia is 5 to 15 meq/L

• A normal subject can lower urinary potassium exertion below 25 to 30 meq per day in the presence of potassium depletion.

• < 15 meq per day is likely representative of extrarenal losses

Acid Base Assessment

• Metabolic Acidosis- with Low urine K exertion in asymptomatic patient is suggestive of Lower GI losses due to Laxative abuse or villous adenoma- with K wasting is most often due to DKA, Type 1 or Type 2 RTA

Acid Base Assessment

• Metabolic Alkalosis:- With low Urine K exertion is due to surreptitious

vomiting or diuretic use- With K wasting and normal BP is most often due to

surreptitious vomiting or diuretic use or to Batter’s syndrome. Urine pH and Urine Cl concentration are helpful

- With K wasting and HTN is suggestive of surreptitious diuretic Rx in Pts with underlying HTN, renovascular disease or primary mineralocorticoid excess

Bartter’s & Gitelman’s Syndrome

• Autosomal recessive disorders• Hypokalemia• Metabolic Alkalosis• Hyperreninemia• Hyperplasia of juxtaglomular apparatus• Hyperaldosteronism• Occasionally hypomagnesaemia

Bartter’s Syndrome

• Named after Dr. Frederic Bartter• Prevalence 1 per million• Often, but not always associated with MR• Pt with a variant of classic Bartter’s syndrome

suffer from the same electrolytes disorders, but also has sensorineural deafness and renal failure

Gitelman’s Syndrome

• After Dr. Hillel Gitelman• Prevalence is 1 per 40000• More benign than Bartter’s

Distinctions between Batter’s & Gitelman’s Syndrome

Bartter’s Syndrome Gitelman’s Syndrome

Localization of defect Ascending limb of Hanle Distal Tubule

Age of Presentation Prenatal, during infancy, early childhood

Mostly late childhood or at adult age

Biochemical difference Serum Mg may be decreased

Serum Mg is decreased

Urinary exertion of Ca is increased

Urinary exertion of Ca reduced

Functional Studies Concentrating capacity severely impaired

Concentrating capacity normal or slightly impaired

GFR may be normal or declining

GFR is normal

Back to our Pt

• Day 4 of hospitalizationMg 1.6K in 24 hour urine was 57 and Ca was 32

• Day 9 of hospitalizationMg 1.8K in 24 hour urine was 81 and Ca was 52

Diagnosis

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