Overview of the Kidney

What are the kidneys again?

Paired, bean-shaped structures located retroperitoneally in the lumbar region, one on either side of the vertebral column

Normally 11-12cm long, 5-7cm wide, 2-3cm thick

There are certain diseases associated with different sized kidneys:

 Large kidneys (>12cm) can be seen in solitary kidney, polycystic disease, diabetes, amyloidosis, acute renal failure, infiltrative kidney (lymphoma), AIDS nephropathy

Small kidneys (<9cm) can be seen in chronic glomerulonephritis, chronic hypertension, bilateral renal artery stenosis, congenital hypoplasia

The outer cortex and inner medulla are both supplied by the renal artery and drained by the renal vein.  Renal disease can affect all areas: cortical renal disease, medullary renal disease, & renal artery disease.

What do the kidneys do again?

3 important ones to remember:
 

1.                   Regulatory Organs

They maintain fluid, electrolyte, & acid-base balance

If the kidneys don’t work, the body will retain fluid  can lead to pulmonary edema & congestive heart failure

 Patients need to be on dialysis to filter out the excess fluid and electrolytes, and also to combat the metabolic acidosis that may occur b/c there is no excretion of the hydrogen ion products in the blood.

2.                   Excretory Organs

As mentioned before as a regulatory function, the kidneys remove various nitrogenous metabolic products in the urine, like creatinine.
 

3.                   Endocrine Organs

The kidneys also produce important hormones: renin, active vitamin D3 and erythropoietin.

 Patients on dialysis need to take supplemental exogenous erythropoietin to maintain appropriate hemoglobin levels in the blood.

What are some major syndromes in nephrology?

The diseases in the left column are discussed in the next 2 hours by Dr. Reddi and then by Dr. Kahn.  The conditions in the right column will be discussed in other lectures.

How do these Renal Diseases Present?

 First of all, appreciate in the picture to the right that the kidneys have an effect on every organ in the body, and therefore various symptoms & signs may be present in different patients with renal disease.

But, there are some common abnormalities of renal disease:

Urine abnormalities

• Hematuria (blood in urine)
   

• Proteinuria (frothy, smoky, bubbling urine due to proteins in urine)

Edema

•  Periorbital (Around the eyelids when the patient wakes up in the AM)
   

•  Generalized
   

• this is the symptom that usually brings the patient to see the physician!

Disturbances with micturition

• Oliguria (<400 ml/day)
   

•  Anuria (<100 ml/day) – this is very dangerous b/c the patient produces little or no urine & retains all the fluids & ions, thus leading to fluid overload, hyperkalemia & metabolic acidosis. They need dialysis!
   

• Nocturia (frequent urination @ night) – this is a tubular problem b/c the renal tubules are responsible for concentrating the urine
   

• Polyuria (>3-4 L/day) – Note this may be due to renal disease or could be due to the patient just drinking a lot of fluids (i.e. polydipsia in diabetes insipidus)

o                    Uremia vs. Azotemia

•  Azotemia just means the serum creatinine levels are higher than normal (normal = 1)
   

• Uremia is when the creatinine levels get so high that the patient becomes symptomatic (fatigue, weakness, anorexia, pain, poor appetite)
   

•  Some patients may experience symptoms @ lower values (like 2.2), whereas other patients may have levels in the 20s and not yet be symptomatic.
   

• Hypertension due to Na and water retention
   

• Renal colic (bilateral flank pain)
   

• Urinary tract infection (dysuria = painful urination)

Electrolyte disorders, like hypo- or hypernatremia, hypo- or hyperkalemia, increased creatinine & BUN, metabolic acidosis

Back to the Excretory System Index