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Continuing Education Activity
Oliguria is a frequently encountered clinical condition that can arise due khổng lồ either prerenal, renal, or post-renal abnormalities. It has various etiologies & management is dependent on the underlying cause(s). In order lớn avoid renal failure, the providers should not only keep in view the etiology và management of oliguria but also the various risk factors and precipitating factors as well. This activity đánh giá the evaluation và management of oliguria & highlights the role of the interprofessional team in improving care for patients with this condition.
Identify the etiology of oliguria.
Describe the appropriate evaluation steps for assessing oliguria.
Summarize the management options for oliguria.
Explain the importance of collaboration & communication amongst the interprofessional team to lớn enhance delivery of care for patients with oliguria.
Access không lấy phí multiple choice questions on this topic.
Oliguria is defined as urinary output less than 400 ml per day or less than trăng tròn ml per hour và is one of the earliest signs of impaired renal function.<1> It had been described early in the literature when Hippocrates identified the prognostic importance of the urinary output. It was in the second century that Galen proposed its significance lớn indicate renal function.<2> Later on, renal failure accompanied by oliguria was described by Heberden as ‘ischuria renalis.’<3><4> According to the Axinh đẹp Dialysis Quality Initiative sầu group, a patient with urinary output <0.3 ml/kg/h for at least 24 hours can be defined khổng lồ be oliguric.<5>
Oliguria can be the result of various causes that can be apparent or subclinical.<1> Oliguria can arise as a result of the normal physiological response of the body toàn thân or due khổng lồ an underlying pathology affecting the kidney or urinary tract. The human body toàn thân has a normal physiological mechanism of conserving fluids và electrolytes in episodes of hypovolemia. These mechanisms are under cchiến bại neurohormonal control & are completely reversible without any subsequent injury to the kidneys.<6> The various etiongắn gọn xúc tích factors can be broadly classified inlớn prerenal, renal, và postrenal causes depending upon the pathophysiology.
Hypovolemia: decreased effective blood volume secondary lớn less fluid intake, bleeding, gastrointestinal fluid loss (diarrhea, vomiting, or nasogastric suction), renal losses (diuretics or glycosuria), third-spacing of fluid (ascites, pleural effusion), trauma, surgery, burns, sepsis, anaphylaxis, hepatic failure, nephrotic syndrome, vasodilatory drugs or anesthetic agents.
Pump Failure: Myocardial failure secondary khổng lồ myocardial infarction, pulmonary embolism, cardiac tamponade, & congestive sầu heart failure.
Vascular: Renal-artery or renal-vein occlusion due lớn thrombosis, thromboembolism, severe stenosis, disrupted renal autoregulation secondary lớn the administration of angiotensin-converting–enzyme (ACE) inhibitors.
Renal or Intrinsic Causes:
Vasculitis, glomerulonephritis, scleroderma, malignant hypertension, or interstitial nephritis.
Acute tubular necrosis (ATN) due to lớn ischemia & nephrotoxic substances, including drugs (e.g., gentamicin, kanamycin, mercury, cisplatin), radiographic contrast agents.
Upper urinary tract obstruction due to ureteral obstruction of one or both sides.
In the postoperative sầu course, as a result of the release of vasopressin as well as the sympathetic stimulation, transient oliguria may be observed.<3><7>
Oliguria is a commonly prevalent condition in hospitalized patients and requires cchiến bại follow up.<8> Episodes of oliguria are observed in nearly half of patients admitted lớn the intensive care unit (ICU).<3><9> Chronic oliguria is commonly seen in patients on long term dialysis.<8>
The most comtháng prerenal cause is reduced blood flow to lớn the kidney secondary to lớn intravascular volume depletion, heart failure, sepsis, or as a side effect of medication. Oliguria secondary khổng lồ prerenal causes usually resolves with the restoration of normal renal perfusion. As a result of the decreased renal blood flow, various neurohormonal pathways are activated, that result in the increased production of renin, angiotensin, aldosterone as well as catecholamines và prostaglandins. Activation of these pathways leads to lớn increased water and salt reabsorption resulting in the production of low quantities of concentrated urine while maintaining adequate glomerular filtration rate (GFR) and renal blood flow (RBF) to meet the metabolic requirements of the kidneys. In case fluid corrections are not done, decremental reductions in GFR & RBF will result in adễ thương renal failure (ARF).
Renal causes of oliguria arise as a result of tubular damage. As a result of the tubular damage, the kidney loses its normal function i.e., production of urine while excreting the waste metabolites. In addition lớn this, direct damage to lớn the renal tubules leads khổng lồ a bachồng leak of filtered uremic metabolites from the tubular lumen into the bloodstream. Hence, in these cases, decreased production of urine leads lớn oliguria.
In post-renal causes, urine production is normal, but as a result of an obstruction in the urinary tract, urine output is greatly diminished.<8>
History và Physical
In a patient with oliguria, a detailed history is required with a focus on past medical history (diabetes, hypertension, heart disease, autoimmune disease, etc.), family history as well as the current medications (potential nephrotoxins).
The patient should be inquired about their occupation, hobbies, and recent travel as well. A thorough physical exam should be carried out lớn assess the hydration status of the patient (skin turgor, mucous membranes) as hemodynamic status can help in the identification of pre-renal causes of oliguria. Alternating episodes of oliguria và polyuria point towards a diagnosis of intermittent urinary tract obstruction.<1> Palpation of the urinary bladder may reveal a distended bladder secondary to lớn urinary retention in axinh đẹp cases. A bedside urinary bladder ultrasound may also be helpful & can instantaneously determine if there is the retention of urine.
After a detailed history is obtained và thorough physical examination is performed, baseline investigative sầu workup should be done, including serum creatinine, urea, serum electrolytes, & blood urea nitrogene. In addition khổng lồ these, urine analysis should be done along with a renal tract/abdominal ultrasound. Urine collection should be done before fluid replacement và drug administration.<1> Certain cases require specific laboratory investigations, including an autoimmune protệp tin (ANA, ANCA, complement levels).<3> An urgent and proper investigation of the patient with oliguria is necessary in order lớn identify any potentially reversible precipitating factor. Prompt investigation & correction avoid the progression of the patient lớn a state of adễ thương renal failure that is associated with its own risks as well as higher morbidity và mortality.<10> The evaluation of the hemodynamic status of the patient may require invasive monitoring of the central venous pressure (CVP) or the pulmonary capillary wedge pressure in cases where the measurements cannot be done with non-invasive methods. Such invasive sầu monitoring may be needed in more critically ill patients.
Urinalysis can aid in distinguishing the causes of oliguria as well. The specific gravity of the urine is >1.02 in prerenal & <1.01 in renal causes. Urinary sodium concentration (mmol/liter) value is <đôi mươi in prerenal causes whereas it is >40 in renal etiologies. Similarly, fractional excretion of sodium (%) is <1% in prerenal & >1% in renal causes. The ratio of urinary lớn plasma creatinine is >40 in prerenal causes, whereas <đôi mươi in renal causes. Urine osmolality is >500 in prerenal and <350 in renal etiologies, & the ratio of urine to lớn plasma osmolarity is >1.5 in prerenal & <1.1 in renal etiologies.<11> The blood urea nitrogen (BUN) khổng lồ creatinine ratio is >20:1 in prerenal disease and <10:1 in renal diseases.
It is due to the fact that the resorptive abilities of the kidney remain normal in prerenal causes. Urinary sediments can also aid in differentiating the prerenal and renal causes of oliguria. Urine samples from patients with prerenal failure often have hyaline & fine-granular casts, whereas brown granular casts with tubular epithelial cells are seen in patients with renal causes.<1>
Renal ultrasound with doppler of renal vasculature can help in the assessment of renal perfusion through the Doppler-based renal resistive index (RI). Imaging, including renal tract ultrasound & CT scan of the abdomen, can help in the identification of the post-renal causes of oliguria. In cases of obstructive sầu uropathy, dilatation of the urinary tract may or may not be present. The dilatation is specifically absent in cases with malignancy, severe dehydration, and the patients who present early for medical attention.<1>
Treatment / Management
A stepwise approach is recommended in the diagnosis và treatment of patients with oliguria. Treatment depends mainly on the underlying etiology.
In post renal causes of oliguria, attention should be directed lớn underlying etiology. Sometimes only simple measures are required to manage those causes, for example, catheter irrigation in case of a clogged urinary catheter, or manipulation in case of a kinked catheter, etc. A bedside bladder ultrasound may be helpful to detect urinary retention & to lớn guide if an indwelling urinary catheter is needed. A urology consultation might be helpful in cases of urinary retention due lớn BPH, tumors, or stones.
The first step is the hemodynamic stabilization of the patient. The amount of fluid is calculated on an individual basis.<1> It should be noted that although hemodynamic stabilization is necessary, volume overloading should be avoided at all costs & treated with diuresis or renal replacement therapy if indicated.<12> Starch products can lead lớn tubular damage và hence should be avoided. For a large volume replacement, balanced crystalloids are recommended. The target for hemodynamic stabilization is achieving the mean arterial pressure (MAP) of 65-70 mmHg in non-hypertensive sầu patients. In addition to lớn all the therapeutic modalities, cthua hourly monitoring of urine output is extremely important lớn gauge treatment accordingly.<3>
If fluid resuscitation fails lớn resolve sầu the oliguria, diuretic therapy should be initiated utilizing a standardized approach. A furosemide găng test (FST) can be done in order khổng lồ assess the patient’s response lớn diuresis. It should be noted that a diuretic challenge should only be given once the patient is euvolemic. Failure of resolution of oliguria with the above sầu step(s) should raise suspicion for evaluation for axinh đẹp kidney injury (AKI). FST is a standardized demo to assess the functional integrity of the tubules và sida in the risk stratification as well as decision making. FST is said khổng lồ be nonresponsive if 1.0-1.5 mg/kilogam of furosemide produces a urine output of 100 ml/h in the first two hours. Nonresponsive FST is associated with a higher stage of AKI. Some studies suggest using 100-200 mg of furosemide initially, and if there is no response, doubling the dose may be considered. If this fails khổng lồ bring any significant improvement adding a thiazide diuretic can also be considered.<1>
One of the most important prerequisites of FST is that the patient should not be hypovolemic, and the heart rate, as well as the blood pressure, should be closely monitored. A recent study has shown that 75% of the patients who are nonresponsive to FST require renal replacement therapy as compared khổng lồ only 13.6% of patients who are FST responsive.<13> A patient responsive lớn diuretics should be managed accordingly.<3><14> If diuretic therapy fails khổng lồ improve sầu the clinical condition, it should be discontinued.<1>
Renal Replacement Therapy:
In oliguric patients, secondary to renal etiology treatment is mainly focused on supportive care & potential renal replacement therapy lớn manage the fluid & electrolyte balance to lớn avoid the development of complications.<1>
In addition khổng lồ focusing on fluid và electrolyte management, adequate protein and caloric intake are necessary. High rates of protein catabolism (200–250 g/day) are observed in patients with ARF, sepsis, or rhabdomyolysis.<1>
The treatment for oliguria should be continued keeping in view the guidelines of AKI treatment. All nephrotoxic drugs should be discontinued, và drugs excreted by the renal system should be carefully reviewed, và their doses should be adjusted.<3> Drugs metabolized by kidneys should be avoided. These drugs include doxorubicin, allopurinol, aminoglycosides, azathioprine, cephalosporins, clofibrate, digoxin, diazepam, meperidine, procainamide, propoxyphene, propranolol, and sulfonamides. In case these drugs are necessary, a dose modification must be done in accordance with the degree of renal injury.<1>
It should be kept in mind that in the setting of oliguria, fluid resuscitation does put the patient at risk of fluid overload, which in turn leads khổng lồ worsening AKI. As a result, overcompensation with fluid is associated with higher mortality when urine output is the determining factor for fluid replacement.<15> Signs of fluid overload include peripheral edema, increased CVPhường, and increased IVC diameter.<16><17> In diuretic responsive sầu patients with fluid overload, diuretic medications are used to manage the fluid overload. On the other h&, in patients who are nonresponsive sầu to diuretics, renal replacement therapy can be used.<3><12>
While evaluating a patient with oliguria, the following differential diagnosis must be kept in mind, và evaluation should be done accordingly:
Pre-renal azotemia: (hemodynamic status of the patient, urine analysis, và doppler based renal resistive sầu index).
Oliguria is one of the first indicators of axinh đẹp renal injury.<8> Oliguric episodes that occur outside the hospital are usually due lớn a single cause & are mostly reversible with a good prognosis. On the other h&, oliguric patients admitted to lớn the hospitals usually have severe renal insufficiency due lớn several underlying precipitating factors. As a result, they have a worse prognosis than that of non-hospitalized patients. Patients admitted in the intensive care unit develop oliguria later in the course of their illness and are secondary to multiple organ failure.<18><19> Hospitalized patients with oliguria have sầu significantly higher morbidity as well as mortality.<1>
Oliguric patients are at higher risk of developing adễ thương renal failure (ARF). 30 to 70 percent of patients with ARF develop infections that are associated with higher morbidity và mortality.<1> However, the mortality risk due lớn oliguria is not completely attributable lớn the development of ARF.<4>
The duration và intensity of oliguria have sầu a great impact on prognosis. As the intensity of oliguria worsens to lớn <0.5 ml/kg/h, the mortality rises significantly.<4>
In patients with axinh đẹp oliguria, one of the most comtháng functional derangements that are observed is the sudden fall in the GRF, leading lớn axinh tươi renal failure. It results in rapid increment in plasma urea và creatinine levels, metabolic acidosis with hyperkalemia, other electrolyte abnormalities, and volume overload. This warrants an expedited hospital admission for management & hence avoidance of the cascade of life-threatening events. Life-threatening complications include:
Electrolyte imbalance: Hyperkalemia, metabolic acidosis, salternative text, & water retention leading khổng lồ pulmonary edema, ascites, or pleural effusions, hyperphosphatemia, or hypocalcemia.
Cardiovascular: As a result of the fluid và salternative text imbalance, congestive heart failure, pulmonary edema, & hypertension usually occur. In some cases, hypotension may be seen, which is a manifestation of other concomitant illnesses such as sepsis. Electrocardiographic (ECG) changes due khổng lồ hyperkalemia can be seen. In about a quarter of cases, arrhythmias may occur due to lớn electrolyte imbalance. Pericarditis is also seen rarely & is a manifestation of uremia.
The primary care provider should consult a nephrologist for an expert opinion as well as a dietician or nutritionist for advice on maintaining appropriate protein and caloric intake. Radiologist consultation may be required in order lớn properly assess renal perfusion through the Doppler-based renal resistive index (RI).<1> In addition khổng lồ this, pharmacy consult is necessary lớn look for the potential nephrotoxic effects of a prescription or any other medication that is primarily renally excreted so that appropriate dosage modification can be made.<20>
Deterrence và Patient Education
The patient should be educated about the importance of maintaining adequate hydration & instructed to avoid the use of any medication without consulting the physician, especially NSAIDs, which are one of the commonly used medications available over the counter for pain relief. The patient should be recommended khổng lồ follow the provider’s advice và get regularly followed up by their physician as well as a nephrologist if the physician suggests.
Prolonged fasting & excessive exercise should be avoided as they can worsen oliguria and can lead lớn rhabdomyolysis. Any catheterized patient should be adequately educated about their catheter care. Monitoring the urine output is one of the determining factors for therapeutic intervention. The patient should be instructed about monitoring the quantity & appearance of urine. The patient should report any color changes, frothing, and sediment formation. In addition, khổng lồ focus on fluid & electrolyte management, adequate protein & caloric intake is necessary.<1>
Pearls và Other Issues
PREDISPOSING RISK FACTORS FOR OLIGURIA:<8>
The following factors have shown to predispose the patient khổng lồ the development of oliguria:
Enhancing Healthcare Team Outcomes
Studies have sầu suggested that early recognition and management play a key role in the prognosis of patients with oliguria; hence cthất bại monitoring should be done in patients with urine output less than 0.5 ml/kg/hour for a period of two consecutive hours.<5>
Radiographic agents used for various diagnostic imaging studies can precipitate oliguria and axinh đẹp renal failure, particularly due lớn their vasoconstrictive effect of renal blood circulation. In a catheterized patient presenting with oliguria, catheter dysfunction should be ruled out.<21> Oliguric episodes in hospitals are usually associated with volume depletion, peri-operative sầu course, diagnostic procedures, & medications.<1>
Special care should be taken to lớn avoid any potential nephrotoxic drugs to a patient with oliguria. These drugs include but are not limited khổng lồ nonsteroidal anti-inflammatory drugs (NSAIDs), aminoglycosides, radiographic contrast agents, general anesthetics, angiotensin-converting–enzyme (ACE) inhibitors, amphotericin B, and numerous chemotherapeutic drugs.<20> In addition khổng lồ all the therapeutic modalities, cthảm bại, hourly monitoring of urine output is extremely necessary khổng lồ gauge treatment.<3>