Acute Kidney Injury (AKI) in Adults

Acute kidney injury is when kidney functioning is affected over a very short duration, that is, hours to days. It is usually a disease that complicates 30% of all ICU admissions. AKI can be Community-acquired AKI, which can develop in cases of Volume depletion, heart failure, Adverse impact of medications (ACEi - Dilation of efferent arterioles), Obstruction of the urinary tract, and Malignancy. AKI can also be acquired from a hospital in the cases of  Sepsis and Major surgical procedures.

It is important to understand that major surgical procedures can induce AKi because the surgery requires a long time, and for that, the duration of the anesthetic effect is needed. This leads to prolonged vasodilation, which causes hypoperfusion.

Serum creatinine is the most reliable way to stage acute kidney disease. However, one must be careful, as serum creatinine can be falsely normal in CKD patients due to less muscle mass.

Thus, two parameters are used to stage acute kidney disease: serum creatinine and urine output.

One can always test for Novel Biomarkers. These are raised in the blood and/or urine, and if a doctor has clinical indications of AKI, they can perform these tests directly.

• Kim-1: Kidney Injury molecule-1
  • It can be checked in urine or plasma
  • It can be used to find out chemotherapy-induced kidney injury
• NGAL: Neutrophil Gelatinase Associated Lipocalin 
  • It can be checked in urine or plasma
• SUPAR: Soluble Urokinase Plasminogen Activating Receptor 
  • Plasma-based test
• Other tests under testing are Cystatin-C, Osteopontin, and Clusterin

Causes of Acute Kidney Injury (AKI) in Adults

• According to the latest medical textbooks, the MC type of acute kidney injury is pre-renal Azotemia. There is no parenchymal damage in this variety. The main causes Include Hypoxia, Decreased cardiac output(cardiomyopathy), and Decreased effective circulating fluid volume.

Few drugs can trigger pre-renal injury type of acute kidney injury, like NSAIDs and ACEi. 

• Another subtype of acute kidney injury is renal/intrinsic, which can have globular, tubular(sepsis might affect tubules), interstitium, or vascular causes.

Glomerular causes include Acute Glomerulonephritis, which has a variable prognosis in different age groups. It has a poor prognosis in adults, while this has shown better results in the pediatric age group.

Vascular causes include hemolytic uraemic syndrome, Thrombotic Thrombocytopenic Purpura, and Malignant hypertension. 

Ischemic Injury to the Tubules can occur in Burns or acute pancreatitis. This event is a precursor for Acute kidney injury. This happens because of cytokine release in capillaries. These cytokines make capillaries leaky, and as a result, Fluid might accumulate in the peritoneal cavity. The treatment in such cases can done with Massive fluid resuscitation. Another complication of such ischemic injury can be abdominal compartment syndrome.

Cisplatin, a drug used to treat lung cancer, causes Contrast-induced nephropathy. Here, the Pre-Serum creatinine is Elevated, and the Post-Serum creatinine is Doubled.

Acute kidney injury can occur in so many different pathways. One such way is Acute Interstitial Nephritis. Drugs like Vancomycin, Methicillin, Proton pump inhibitors, and NSAIDs can cause it. It usually has very common symptoms like Fever, AKI, Rash, and Eosinophiluria(eosinophils in urine)

Renal Vein Thrombosis is another very prominent cause of AKI. It causes not only AKI but also Unilateral Kidney enlargement. This hyperplasia or enlargement is best diagnosed with Renal angiography.

• Post Renal AKI

It can be caused 

• Benign prostatic hyperplasia- enlargement of the prostate gland, seen in elderly male patient
• Bladder Outlet Obstruction
• Scleroderma - Bilateral ureteral fibrosis Caused by the drug - Bleomycin 

It has some basic clinical symptoms like Nausea, vomiting, and Hiccups but may even progress to some serious symptoms like Progressive decline in GFR leading to hypertensive crisis, Volume expansion causing Pedal edema & Pulmonary edema, and Oliguria (decreased urine output) or Anuria(no urine output).

The diagnosis of a post-renal type of Acute kidney injury can be made based on a WorkUp that includes kidney function tests(KFT): BUN & Elevated Serum creatinine, serum Electrolytes, Uric acid—gross elevation in TLS patients, and ABG—metabolic acidosis.

When the urine of a patient with post-renal AKI is Microscopically examined, muddy brown granular casts, Dysmorphic RBCs, and Eosinophiluria are seen.

There are multiple ways to treat acute kidney disease; generally, all treatments are done symptomatically. 

First and foremost, Fluid management, where the urine output is meticulously measured. The patient is checked for electrolyte imbalance with the help of a serum electrolyte blood test. Firstly, chloride levels are checked. If they are low, normal saline is used, whereas if they are high, the patient is supplemented with Ringer lactate.

Soda bicarbonate and Normal saline are used to initiate Forced alkaline diuresis. This prevents primary tubular damage.

Treatment with Furosemide is also initiated with a Bolus of 200 mg.

A very important treatment method is also used, which has helped so many people with acute kidney injury lead a normal life. This treatment is known as Hemodialysis. In simple terms, hemodialysis is a method in which all the accumulated impurities in the body, which were earlier cleared by the kidney, are cleared from the blood. However, this method cannot be used in all patients, and there are certain indications for it:

• Metabolic Acidosis where PH > 7.1 despite correction
• Electrolyte imbalance - Hyperkalemia despite correction
• Insufficiency - eGFR < 10 ml/min 
• Volume Overload - Despite medication
• Uremic pericarditis - Absolute indication 
• Encephalopathy 

Because hemodialysis is a lifelong process and requires multiple visits to the hospital thus, a Double lumen catheter is placed in either the Internal jugular vein, Subclavian vein, or Femoral vein.

The Most common complication of hemodialysis is Hypotension. 

In hemodynamically unstable patients, Continuous veno-venous hemodialysis is used for 24 hrs. 

In conclusion, we know that Acute kidney injury can be caused in multiple ways and can even complicate many ICU-admitted patients. However, this can be avoided if acute kidney injury is diagnosed well in advance and correct treatment is initiated. Hemodyliasis is the best treatment for Acute Kidney Injury with comorbidities. 

Dr. Deepak Marwah explains this topic of acute Kidney injury very well in his lecture videos on PrepLadder.

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