Azotemia

What is Azotemia?

Azotemia is a medical condition that occurs when there’s too much nitrogen waste (substances like BUN and creatinine) in your blood. This happens due to the kidneys not being able to filter waste products as well as they should. It’s a common characteristic of both an acute (sudden) and chronic (long-term) kidney injury.

In the context of acute kidney injury (AKI), which is a sudden episode of kidney failure or kidney damage, azotemia is significant. There are three subcategories of azotemia: prerenal, intrinsic, and post-renal. Several guidelines are employed to diagnose AKI, such as the RIFLE criteria (2004), AKIN criteria (2007), and the KDIGO system (2012). Typically, an AKI diagnosis is made when there’s an increase in creatinine (a waste product in your blood) levels. Tests like urinalysis, urine electrolytes, metabolic panel, and a kidney ultrasound are done for diagnosis. The results from these tests help determine the type and cause of the AKI, leading to appropriate treatment.

When azotemia starts showing noticeable symptoms and physical signs, along with the presence of abnormal biochemical findings, it becomes what is referred to as uremia.

What Causes Azotemia?

Azotemia, a condition characterized by high levels of nitrogen compounds in the blood, has different types each caused by unique factors.

* Prerenal azotemia occurs when there’s something disrupting the blood supply before it gets to the kidneys. This interruption in blood flow can be due to a range of causes including dehydration, severe injury leading to blood loss, extensive burns, certain heart and liver conditions, as well as severe forms of shock, which all lead to inadequate blood volume.

* Intrinsic azotemia is the result of damage within the kidney’s structure including the small filters (glomeruli), the tubes in the kidney (renal tubules), the tissue around these tubes (interstitium), and the blood vessels in the kidney (renal vasculature). This damage might be due to swelling of the blood vessels (vasculitis), exposure to harmful substances or drugs, infections, or injuries arising from insufficient blood flow.

* Post-renal azotemia is linked to problems in the tubes (ureters) that carry urine from the kidneys to the bladder and within the bladder itself. Commonly, these problems involve some type of blockage, observable in patients with risk factors such as frequent urinary tract infections, kidney stones, kidney swellings (hydronephrosis) and prostate gland enlargement (benign prostatic hyperplasia).

Risk Factors and Frequency for Azotemia

Azotemia, though common and linked to a high risk of death, remains a medical condition that is partially understood. It accounts for between 8% and 16% of hospital admissions. The International Society of Nephrology aims to eliminate all preventable deaths from AKI, a related condition, by 2025.

A global study was conducted in 2014 across 72 countries to better understand AKI and improve treatment strategies. Despite differing between countries, some of the major causes of AKI were found to be dehydration, shock, infection, sepsis, heart disease, and certain toxic medications. The study emphasized the benefits of worldwide data collection to inform a global approach to treating this disease.

• Azotemia is a fairly common condition that results in 8% to 16% of hospital admissions.
• The International Society of Nephrology plans to stop all avoidable deaths from AKI by 2025.
• A major research was conducted in 2014 across 289 centers and 72 countries to gather data about AKI.
• The death rate within seven days of diagnosis was found to be 10 to 12%, regardless of the country’s income level.
• Dehydration, shock, infection, sepsis, cardiac disease, and toxic medications were identified as the main causes of AKI.

Signs and Symptoms of Azotemia

If you’re being evaluated for azotemia or acute kidney injury (AKI), there are certain aspects your doctor will look into to figure out what’s wrong and how best to treat you. These include:

• Assessing your hydration level by checking your mucous membranes, skin elasticity, presence of edema or swelling, any evidence of liver-related fluid reflux, sounds in your lungs, or fluid accumulation in the abdominal cavity
• Looking for signs of infections like fever, chills, sweating, cough, congestion, nausea, vomiting, diarrhea, frequent or painful urination, or blood in urine

In addition to these general inquiries, some specific findings can indicate different types of kidney problems. These could be:

• Prerenal findings like history of sepsis or other forms of shock, burns, bleeding, dehydration, skin elasticity, worsening fluid accumulation due to loss of fluids from the blood vessels (oedema and ascites), or low blood pressure
• Intra-renal findings like a history of using medication toxic to the kidneys, exposure to contrast agents, or poorly controlled high blood pressure or diabetes
• Post-renal findings that could include side or lower back pain possibly due to kidney infection; colicky pain suggesting kidney stones; a bulky-feeling prostate, trouble urinating, or total absence of urine possibly related to an enlarged prostate; a history of smoking possibly suggesting bladder cancer; or spine injury possibly leading to a ‘neurogenic’ bladder (disorder).

Testing for Azotemia

Azotemia, a medical condition marked by high levels of nitrogen waste products in the blood, can be diagnosed and evaluated through several laboratory and radiographic tests. These include basic metabolism and urine tests, along with ultrasound, CT scans of the abdomen and pelvis, or a renal Doppler exploration.

A diagnosis of Azotemia is typically made if the blood urea nitrogen (BUN) level is higher than 21 mg/dL. Depending on test results, doctors can classify the condition as prerenal, intra-renal, or post-renal azotemia. Each has distinct markers.

Prerenal azotemia, which occurs before the kidney, is indicated by a high BUN to creatinine ratio (over 20:1), low levels of sodium or urea waste flushed out through urine (less than 1 and 35% respectively), increased urine concentration (above 500 mOsm/kg), and urine test showing hyaline (a certain kind of protein) casts.

Intra-renal azotemia happens within the kidney and is signaled by a BUN to creatinine ratio less than 20:1, higher waste levels (above 2 for sodium and above 50% for urea), a decreased urine concentration (less than 300 mOsm/kg), and a urine test showing cellular debris, muddy brown casts, red cell casts, eosinophils (a type of white blood cell), and proteinuria (excess protein in urine).

Post-renal azotemia takes place after urine has passed the kidney. This is indicated by a BUN to creatinine ratio less than 20:1, high sodium flushing levels (greater than 2), decreased urine concentration (less than 300 mOsm/kg), and white blood cell casts in the urine test. Imaging could show inflammation of the kidney and its pelvis (pyelonephritis), kidney stones (nephrolithiasis), or bladder mass.

Treatment Options for Azotemia

The main goal when treating azotemia, a condition marked by a high level of nitrogen waste in the blood, is to address the root cause of the issue. For conditions that occur before the kidneys (prerenal), replenishing the body’s fluids using an IV and possibly using medicine to improve blood flow are vital. This helps ensure that the kidneys are well-supplied with blood and helps maintain the health of the blood vessels and tubules in the kidney.

In cases where the issue lies in the kidneys themselves (intrinsic renal), the treatments can vary widely. Some of the key steps include stopping any harmful substances, avoiding further usage, and then hydrating the patient. This allows the kidneys to recover. High blood pressure and diabetes are two common causes of kidney damage if not properly controlled. Therefore, managing blood pressure and blood sugar levels are key to protecting the kidneys.

For conditions that affect the areas after the kidneys (post-renal azotemia), the main treatment is removing any blockage and rehydrating the patient. A urologist might need to examine the patient, and it might be necessary to place a catheter.

To ensure that the kidneys are working well, doctors monitor the patient’s blood urea nitrogen to creatinine ratio (BUN/Cr) and urine output. A minimum urine output of 0.5 mL per kilogram of body weight per hour is seen as a good sign of stable kidney function.

What else can Azotemia be?

If you have a high level of BUN (blood urea nitrogen) in your blood test, it means your kidneys might not be working properly. There are quite a few reasons why this could be happening:

• Bleeding in your stomach or intestines
• If you’re taking steroids
• Ketoacidosis, a dangerous build-up of acids in your blood often caused by poorly managed diabetes
• Your body is breaking down more proteins than usual
• Congestive heart failure, a condition where your heart isn’t pumping blood as well as it should
• You’re being fed through a vein because you can’t eat by mouth (Hyperalimentation or TPN)

These things can all lead to a higher level of BUN, but every case is different. It’s important to consult your doctor to find out what’s causing your BUN level to be high.

What to expect with Azotemia

Treatment for azotemia, a condition related to kidney function, often has positive results. What’s amazing about kidneys is their capacity for cell repair. When kidney injury is resolved and blood flow is restored, the kidneys work towards repairing cells, migrating, and multiplying them to restore normal kidney function.

If kidney dysfunction advances, it may lead to chronic kidney disease (CKD) or, in more severe cases, end-stage renal disease (ESRD). In these instances, patients often require dialysis to assist their kidney function.

Possible Complications When Diagnosed with Azotemia

One of the complications tied to high BUN (Blood Urea Nitrogen) levels usually results from an overproduction of nitrogen waste, particularly in cases of kidney failure. This excess waste can be toxic and may lead to a condition called uremia. Uremia can have a range of side effects such as:

• Problems with blood platelets causing bleeding
• Changes in brain function, known as encephalopathy
• Peripheral neuropathy, a problem with nerve function outside the brain and spinal cord
• Nausea and vomiting
• Lowered body temperature, or hypothermia
• Itchy skin

If someone has uremia, it’s a sign that they urgently need to have their blood filtered through a machine, a process called hemodialysis. Drugs like Allopurinol and Rasburicase can help manage the levels of uric acid in the body and also protect the kidneys.

Preventing Azotemia

Good primary healthcare and patient awareness play a key role in controlling related conditions that can lead to azotemia or Acute Kidney Injury (AKI). Diabetes and high blood pressure are the two major conditions that pose a significant risk to kidney health. It’s equally important for patients to avoid exposure to infections and maintain proper hydration. Adopting these practices can help ensure the kidneys remain healthy and function effectively.