What causes elevated pH in urinalysis?

From the Guidelines

Elevated pH in urinalysis is primarily caused by urinary tract infections (UTIs) with bacteria that produce urease, which breaks down urea into ammonia and raises urine pH, as well as other factors such as a vegetarian diet high in fruits and vegetables, certain medications, and metabolic or respiratory alkalosis. The causes of elevated pH in urinalysis can be multifactorial, including:

• Urinary tract infections (UTIs) with urease-producing bacteria
• Vegetarian diet high in fruits and vegetables, which can increase urine pH 1
• Certain medications like acetazolamide and sodium bicarbonate
• Metabolic or respiratory alkalosis
• Prolonged storage of urine samples at room temperature
• Renal tubular acidosis (RTA), including Bartter syndrome, which can present with hypokalemic alkalosis and nephrocalcinosis 1 Normal urine pH typically ranges from 4.5 to 8.0, with values above 8.0 considered elevated. Patients with persistently alkaline urine may be at increased risk for certain types of kidney stones, particularly calcium phosphate and struvite stones, as the solubility of these stones decreases at higher urinary pH values 1. If elevated urine pH is found without symptoms, it may not require treatment, but the underlying cause should be identified, especially if UTI is suspected. Proper collection technique and prompt testing of urine samples can help ensure accurate pH readings. In some cases, potassium citrate may be offered to patients with uric acid and cystine stones to raise urinary pH to an optimal level 1.

From the FDA Drug Label

When Potassium Citrate is given orally, the metabolism of absorbed citrate produces an alkaline load. The induced alkaline load in turn increases urinary pH and raises urinary citrate by augmenting citrate clearance without measurably altering ultrafilterable serum citrate The increase in urinary pH also decreases calcium ion activity by increasing calcium complexation to dissociated anions. The rise in urinary pH also increases the ionization of uric acid to the more soluble urate ion In patients with severe renal tubular acidosis or chronic diarrheal syndrome where urinary citrate may be very low (<100 mg/day), Potassium Citrate may be relatively ineffective in raising urinary citrate. In patients with renal tubular acidosis in whom urinary pH may be high, Potassium Citrate produces a relatively small rise in urinary pH.

The cause for elevated pH in urinalysis can be Potassium Citrate therapy 2, as it increases urinary pH by producing an alkaline load. Other possible causes of elevated urinary pH include:

• Renal tubular acidosis 2, where urinary pH may be high
• Chronic diarrheal syndrome 2, where urinary citrate may be very low
• Other conditions that increase urinary citrate or produce an alkaline load.

Note that the FDA label does provide direct information on the cause of elevated pH in urinalysis.

From the Research

Causes of Elevated pH in Urinalysis

• Renal tubular acidosis (RTA) can cause elevated pH in urinalysis, as the kidneys are unable to maintain normal acid-base homeostasis due to tubular defects in acid excretion or bicarbonate ion reabsorption 3.
• Distal RTA (type 1) is characterized by impaired acid excretion, which can lead to an elevated pH in the urine 3, 4.
• Certain diets, dietary supplements, and medications can also affect urine pH, leading to elevated levels 5.
• Potassium citrate supplementation can help correct urinary abnormalities, including elevated pH, in patients with distal RTA 6.
• Other factors, such as hydration status and exercise, can also influence urine pH, although the exact mechanisms are not fully understood 5.

Underlying Mechanisms

• The kidneys play a crucial role in maintaining acid-base homeostasis, and defects in acid excretion or bicarbonate reabsorption can lead to elevated urine pH 3, 4.
• The use of certain medications, such as bicarbonate therapy, can also affect urine pH, although the benefits and drawbacks of such therapy are still debated 7.
• The relationship between diet, hydration, and exercise and urine pH is complex and requires further study to fully understand the underlying mechanisms 5.