Dr. NK Hase delivers a masterclass on kidney diseases, exclusive in this 4-part weekly series for M3 India. In this first part, he writes about varied presentations of kidney diseases in patients and steps involved in making an accurate diagnosis. You can also drop in your queries at the end of the article. Dr. Hase will address them in a separate article, once this series concludes.

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Traditionally, we use a syndromic approach in nephrology to answer the above questions. Common syndromes we diagnose are acute nephritic syndrome, nephrotic syndrome, rapidly progressive glomerulonephritis, acute kidney injury, chronic kidney disease, acute interstitial nephritis, tubular syndromes, obstructive nephropathy and syndrome of hypertension.

These syndromes often overlap and the clinicopathologic correlation is also complicated. I propose to use a Neurologist's approach to diagnose kidney diseases. While dealing with kidney diseases, a physician will have to find answers to the following questions:

1. Is kidney disease present? If yes-
   1. Where is the site of the lesion? (anatomical diagnosis- is it vascular, glomerular, tubular, tubulointerstitial, ureteral, or bladder)
   2. What is the aetiology of the lesion? (pathogical diagnosis)
2. Does the patient have kidney function impairment? If yes-
   1. Is it acute kidney injury (AKI), or acute kidney disease (AKD) or chronic kidney disease (CKD)?
   2. What are the other complications and comorbidities present?

This simple approach will help to decide the complete plan of management and prognosis. We can divide the kidneys into different anatomical compartments-

• Prerenal
• Renal
• Post-renal

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Prerenal

The kidney is supplied by renal arteries. Each minute, 1200 ml blood (20% of cardiac output) passes through kidney for filtration. Any systemic condition leading to hypoperfusion of kidneys resulting in decreased Glomerular Filtration Rate (GFR) will be called a prerenal lesion.

Intrinsic kidney diseases (Intrarenal)

They can be localised as:

• Glomerular
• Tubular
• Tubulointerstitial
• Vascular lesions

Post-renal

Lesions can be localised to conducting system:

• Pelvis
• Ureter
• Bladder
• Urethral

Functional impairment

This can be localised as:

1. Prerenal failure: It is caused due to decreased GFR due to decreased kidney perfusion. Glomeruli and tubules are structurally normal and it is potentially reversible.
2. Acute Kidney Injury (AKI): It is caused due to abrupt onset decrease in GFR resulting in retention of nitrogenous waste products and disturbances in maintenance of water and electrolyte balance. AKI onset is within hours to days. The patient recovers within 2 to 7 days.
3. Acute Kidney Disease (AKD): AKI which does not recover within 7 days, progresses, and takes up to 90 days for recovery is called as AKD.
4. Chronic Kidney Disease (CKD): Structural damage and functional impairment that persist beyond three months is called as CKD. It is usually progressive and irreversible damage.

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How to come to a diagnosis? What are the steps involved?

Like any other branch in medicine basic steps involved in diagnosis are:

• Detailed history
• Physical examination
• Investigation

A patient with kidney diseases can present in different ways to different specialties.

1. The patient may be asymptomatic and the disease may be detected during investigation like urine analysis and renal chemistry: BUN, serum creatinine and electrolytes at pre-employment check up or health check up.
2. The patient may not have symptoms directly related to the kidney or urinary tract and present with non-specific symptoms and signs due to failing renal excretory and metabolic functions. These symptoms are usually late and in the advanced stages.
3. The patient may present to a Gastroenterologist with nausea, vomiting, loss of appetite, weight loss, or due to uraemia.
4. The patient may have fatigue, exertional breathlessness and palpitation due to anaemia and present to a Primary Care Physician, Hematologist or Cardiologist.
5. The patient may present to an Orthopaedic Surgeon with bone pain and deformities due renal osteodystrohy (particularly seen in children).
6. There may be symptoms and signs resulting from impaired salt- and water-handling like oedema, puffiness of face and high blood pressure.
7. Occasionally, the patient may present with symptoms locally arising from the kidney and urinary tract, like flank pain, haematuria, urgency frequency, nocturia, and slow stream.
8. The patient may have a systemic disease which contributes to structural and functional impairment of the kidneys like diabetes, Systemic Lupus Erythematoses (SLE),vasculitis and primary or secondary amyloidosis,.

Diagnosing kidney diseases requires high index of suspicion

Majority of the patients will require urinalysis, biochemical, and radiological investigations. Symptoms, signs, and investigations are analysed to formulate.

• Anatomical diagnosis: Vascular lesion, glomerular, tubular, tubulointerstitial, or post-renal lesions
• Aetiological diagnosis: For instance, in renovascular hypertension due to renal artery stenosis, aetiology will be atherosclerosis or fibromuscular dysplasia
• Renal impairment: Is it present or absent? If present, is it AKI, AKD or CKD?
• Complications and comorbidities: Azotemia, uraemia, fluid overload, metabolic acidosis, cardiac failure, and anaemia

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In the next part, Dr. NK Hase will write on diseases affecting the various compartments, individual clinical manifestations and diagnosis for each.

Disclaimer- The views and opinions expressed in this article are those of the author's and do not necessarily reflect the official policy or position of M3 India.

The author Dr. NK Hase is a Director clinical Nephrology & Transplant working at Jupiter Hospital, Thane and former Professor & Head of Department of Nephrology Seth GS Medical College and KEM Hospital, Mumbai.