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Date of last update: 8/13/2017.

Forum Name: Urology Topics

Question: Enlargened Kidneys

 dotdotdot - Wed Jun 23, 2010 5:47 am

Since last year, I have been to the hospital a few times to get my kidneys checked up on. Since my last test they have said that my kidneys have slightly enlarged over a three month period, however not large enough to draw any conclusions. I am having another test at end of October. I am wondering if there is any need for alarm. The specialist has stated that I may have had it since birth.

 Dr.M.Aroon kamath - Thu Jul 01, 2010 10:55 pm

User avatar Hi,

Renal "enlargement" is a rather vague term. It may imply just an increase in the size due to any reason (increase in the renal parenchyma, dilatation of the pelvi-calyceal system or both). Or, it may mean, as it generally does, renal hypertrophy (commonly 'compensatory' hypertrophy).

Renal enlargement (almost always renal hypertrophy) can be
- focal (when a part of a kidney hypertrophies to compensate for disease in the rest of the kidney), or
- uniform.

It can also be
- unilateral or
- bilateral.

It can also be
- microscopic (mostly noted in experimental situations) or
- macroscopic.

When the work load presented of an organ increases, the normal physiological response is to increase its function. To compensate for increases in work load, some organs respond by an increase in the number of their functioning units. For example, in the case of the breast during lactation, new acini develop, and in a like fashion, chronic hypoxia induces an increase in the number of erythrocytes.

In some organs, there is a predetermined limit to the total number of functioning units. For example, in the kidneys and lungs, the number of nephrons and alveoli is set early in life, and the number of functional units can't increase (irrespective of the demands). Similarly situation is seen in the heart and skeletal muscles. The inability to initiate functional unit regeneration “forces” these organs to hypertrophy (to increase the physical size of their units to increase their work capacity).

What exactly is the signal for initiation of hypertrophy is not clear. In the heart it is thought to be a "pressure-overload" hypertrophy.In the kidneys, a similar situation may exist- increased glomerular hydrostatic pressures (Glomerular hyperfiltration). Compensatory renal hypertrophy primarily involves the proximal tubules.

In the clinical situation, renal hypertrophy that is frequently encountered is "compensatory renal hypertrophy", which is usually unilateral (congenital absence of a kidney, removal of a kidney or diffuse disease affecting one kidney) resulting in compensatory hypertrophy in the remaining kidney.

Some of the oher causes mentioned in the literature are
- hyperglycemic-dependent renal hypertrophy in diabetics (bilateral),
- renal hypertrophy induced by hyperthyroidism, &
- potassium deficiency causing renal hypertrophy in experimental animals.
Best wishes!

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