Chapter 5. Kidney diseases

Formulating a diagnosis

Components of the diagnosis: etiology; morphological type; clinical form; activity; CKD; complications

Glomerulonephritis (GN ) is a group of immune kidney diseases characterized by primary glomerular damage and subsequent involvement of interstitium in the pathological process with a tendency to progression, transition to nephrosclerosis and development of chronic renal failure syndrome.

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Chronic glomerulonephritis (CGN) is a chronic immune inflammatory kidney disease with a long-term persistent or recurrent urinary syndrome and a gradual deterioration of renal functions.

CGN occupies the third place in chronic kidney disease structure, it can develop at any age, but is more common in children 3–7 years old and men aged 20–40 years.

Etiological factors of CGN are infections, tumors, systemic diseases, me­di­cations (antibiotics, NSAIDs, rifampicin, vaccines, serums, lithium salts, etc.), toxic substances (gold, mercury, etc.). But autoimmune idiopathic types are more common.

CGN pathogenesis is based on immune damage to the glomeruli. The me­cha­nisms of CGN development are the influence of immune complexes on kidney structures: basement membrane of glomerular capillaries, deep cells, podocytes, where circulating immune complexes are deposited and formed in situ, as well as antibodies to determinants of basal glomerular capillary membrane are produced. Proliferation and activation of mesangial cells play an essential role in accumulation and structural change of extracellular matrix, which results in glomerular sclerosis.

Non-immune factors are also important for further progression of glome­ru­lonephritis:

• changes in hemodynamics (intraglomerular hypertension and hyperfiltration);
• tubulointerstitial changes, which are affected by proteinuria (release of albumin and transferrin);
• hyperlipidemia.

Etiology

There are primary or “idiopathic” and secondary CGN:

• collagenoses (systemic lupus erythematosus, rheumatoid arthritis);
• systemic vasculitis;
• paraneoplastic processes (solid tumors, lymphoma);
• systemic infections (HCV, HBV, EBV, infectious endocarditis);
• drug-induced injuries (antibiotics, NSAIDs, heavy metals).

Morphological type

Damage to the glomerular capillary wall:

• minimal change glomerulonephritis;
• focal segmental glomerulosclerosis (FSGS);
• membranous nephropathy.

Damage to the mesangial region:

• membranoproliferative (Berger’s disease or IgA-nephropathy);
• mesangiocapillary (membranoproliferative) GN.

Simultaneous damage to the mesangium and capillary wall of the glomerulus:

• diffuse proliferative GN;
• extracapillary (“semilunar”) GN;
• sclerosing GN.

Clinical form

• Latent.
• Hematuric.
• Nephrotic.
• Hypertonic.
• Mixed.

CGN with isolated urinary syndrome (latent form). This form accounts for up to 50% of all CGN cases. The disease is asymptomatic (with no edema and hypertension). During examination, proteinuria (less than 1–2 g/day), microhematuria, leukocyturia, cylindruria (hyaline and RBC casts) are detected. CRF development is slow.

Hematuric form. It is characterized by changes in the urine (microhema­turia, indolent proteinuria). AH and edema are absent. CRF development is slow. The most common clinical variant of hematuric form is IgA-nephropathy, which is observed mainly in young males. Episodes of macrohematuria are characteristic, accompanied by pain in the lumbar region, associated with infections of upper respiratory and gastrointestinal tract. The difference from acute post-infectious glomerulonephritis is the occurrence of renal symptoms simultaneously with provoking factors. Proteinuria is non-critical, edema is minimal or absent, no hypertension. In most cases, the disease is benign

Hypertonic form. In clinical presentation, symptoms of increased blood pressure are predominant: headache, visual impairment — dimout, “floaters”, pain in precardial region is possible. Urinary syndrome is expressed mildly (microhematuria, proteinuria up to 1–2 g/day), hypertension is intermittent. Unlike hypertension, urinary syndrome in case of chronic glomerulone­phritis is observed from the onset of the disease. With progression of the disease, hypertension gradually becomes resistant to drug therapy.

Nephrotic form. This form is characterized by nephrotic syndrome and edema development (daily proteinuria >3.5 g/day, hypoproteinemia, hypo­albuminemia, hyperlipidemia). The main laboratory sign is massive proteinuria. The higher the proteinuria, the lower the albumin level in blood. Hypoalbuminemia leads to a decreased oncotic plasma pressure, edemas occur. A decrease in intravascular fluid volume leads to RAAS activation and increased tonicity of sympathetic part of autonomic division of nervous system, anti­diu­retic hormone is released, synthesis of atrial natriuretic factor is suppressed, sodium and water retention occurs. A significant loss of transferrin in the urine leads to microcytic hypochromic anemia associated with nephrotic syndrome.