From the Guidelines
Polyuria and Overactive Bladder (OAB) are distinct urinary conditions with different underlying mechanisms and symptoms, and the key to differentiating them lies in understanding the primary issue - whether it's the kidneys' inability to properly concentrate urine in polyuria or detrusor muscle overactivity in OAB, as highlighted in the 2019 guideline amendment by the American Urological Association 1.
Key Differences
- Polyuria refers to the excessive production of urine, typically defined as urinary output exceeding 3 liters per day in adults, characterized by increased urine volume rather than frequency.
- OAB is a symptom complex characterized by urinary urgency, usually accompanied by frequency and nocturia, with or without urgency incontinence, resulting from detrusor muscle overactivity rather than increased urine production.
Diagnostic Considerations
- The differential diagnosis of nocturia, a common symptom in both conditions, includes nocturnal polyuria, low nocturnal bladder capacity, or both, as noted in the 2019 guideline amendment 2.
- A careful history, physical exam, and urinalysis are minimum requirements for diagnosing OAB and excluding other disorders, as emphasized in the 2012 guideline by the American Urological Association 3.
Treatment Approaches
- Polyuria management targets the underlying cause, such as glucose control in diabetes mellitus or vasopressin replacement in diabetes insipidus.
- OAB treatment includes behavioral modifications, pelvic floor exercises, anticholinergic medications like oxybutynin or solifenacin, beta-3 agonists like mirabegron, or neuromodulation therapies in severe cases, as recommended in the 2019 guideline amendment 1.
Clinical Decision-Making
- The choice of treatment should be based on a shared decision-making process between the physician and patient, considering the benefits and risks of each treatment alternative, as suggested in the 2013 evaluation and treatment of lower urinary tract symptoms in older men 4.
- Patients with bothersome symptoms should be evaluated and treated based on the results of initial evaluation, with further tests and specialist referral as needed, as outlined in the 2012 guideline 5.
From the Research
Definition and Characteristics
- Polyuria is characterized by a urine output that is inappropriately high (more than 3 L in 24 h) for the patient's blood pressure and plasma sodium levels 6.
- Overactive bladder (OAB) is a syndrome characterized by unstable bladder contractions, resulting in urinary urgency, frequency, and nocturia in the absence of detectable disease 7.
Diagnostic Approach
- Polyuria is diagnosed based on pathophysiology, including urine osmolality, estimation of free water clearance, and measurement of electrolytes in blood and urine 6.
- OAB is a diagnosis of exclusion that begins with a targeted history and examination of the urogenital system, with the aim of assessing the burden of disease on the patient 7.
- The diagnosis of OAB relies on subjective assessment of symptoms by the patient, including urgency, frequency, and nocturia 8.
Key Differences
- Polyuria is primarily characterized by an excessive urine output, whereas OAB is characterized by symptoms of urgency, frequency, and nocturia 6, 7.
- Polyuria can be caused by various factors, including psychogenic polydipsia, diabetes insipidus, and chronic kidney disease 9, whereas OAB can be caused by neurologic illness or injury, bladder outlet obstruction, and detrusor hyperactivity 10.
Similarities and Considerations
- Both polyuria and OAB can present with symptoms of frequency and nocturia, making it essential to rule out other potential diagnoses, such as urinary tract infection and bladder cancer, before making a diagnosis of OAB 8.
- The symptoms of OAB can be similar to those seen in other conditions, highlighting the importance of a thorough diagnostic approach to differentiate between polyuria and OAB 7, 8.