Chronic kidney disease: Clinical sciences

Chronic Kidney Disease, or CKD, refers to an impairment in renal function that persists for 3 or more months. This functional impairment occurs most commonly when comorbid conditions, like hypertension or diabetes mellitus, cause progressive sclerosis of the nephrons. Most commonly, CKD is classified by underlying cause, the degree of albuminuria, and the estimated glomerular filtration rate, or eGFR for short, which can help determine appropriate treatment and assess prognosis.

Now, if you suspect CKD, you should first perform an ABCDE assessment to determine if your patient is unstable or stable.

If the patient is unstable, stabilize the airway, breathing, and circulation. Next, obtain IV access and provide supplemental oxygen to maintain adequate oxygenation. Finally, put your patient on continuous vital sign monitoring, including blood pressure, heart rate, and pulse oximetry, and if necessary, obtain dialysis access as well.

Here’s a clinical pearl to keep in mind! Patients with CKD that present as unstable will often have end-stage renal disease and may have missed scheduled dialysis. In that case, they might present with hyperkalemia, metabolic acidosis, fluid overload, as well as uremia. Moreover, in uremia, your patient might develop uremic frost, which occurs when serum BUN is elevated to the extent that urea seeps through the skin in the sweat and crystallizes, giving a frosty appearance. Additionally, they might have pericardial friction rub, which suggests the development of uremic pericarditis; or they may develop confusion and asterixis, indicating uremic encephalopathy. Finally, keep in mind that after initial stabilization, these patients will require urgent dialysis as a definitive treatment.

Okay, now let’s go back to the ABCDE assessment and discuss stable patients.

In stable individuals, you should first obtain a focused history and physical examination, and order labs, including CMP. History often reveals nonspecific symptoms, such as fatigue or anorexia, while past medical history often includes diabetes, hypertension, familial conditions like polycystic kidney disease, or frequent use of nephrotoxic medications like NSAIDs. On the other hand, physical exam might reveal elevated blood pressure and swelling of the feet and ankles, while labs usually show elevated serum creatinine, or at least elevated from their previous baseline.

At this point, you should suspect CKD, so your next step is to calculate the eGFR.

If the eGFR is less than 60 and has remained below 60 for 3 months or more, you can confidently diagnose CKD.

Alright, now that you’ve diagnosed CKD, the next thing to do is assess the underlying cause, first by measuring blood pressure, then ordering labs, including a hemoglobin A1C, and a urinalysis with microscopy. In some cases, imaging, such as a renal ultrasound, or even invasive studies, like a renal biopsy may be needed to identify the underlying cause.

A blood pressure greater than 140/90 mmHg suggests the diagnosis of hypertension, while a hemoglobin A1C greater than 6.5% is diagnostic for diabetes. On the other hand, if urinalysis with microscopy reveals proteinuria, cell casts, and maybe even hematuria, you should suspect the presence of glomerular disease.

Now, here’s a high-yield fact to keep in mind! The workup for glomerular disease in the setting of CKD can be quite extensive, and includes anti-neutrophil cytoplasmic antibodies, like c-ANCA and p-ANCA; protein electrophoresis, such as SPEP and UPEP; autoantibodies, like antinuclear antibodies and rheumatoid factor; as well as infectious agents, like HIV, Hepatitis B, and Hepatitis C.

Next, renal ultrasound can help you identify structural causes of CKD, like cysts in the case of polycystic kidney disease;

while a renal biopsy will help histopathologically identify the specific cause of glomerulonephritis, like the presence of a crescentic pattern in Goodpasture syndrome.

Ok, now that you’ve identified the underlying cause, the goal is to treat it, if possible, to hopefully slow down the progression of CKD.

Once you are done with identifying the cause, next, you need to assess renal function.