Hematological Tests And Radiological Investigations In Nephrology
Blood Urea Investigation
Normocytic normochromic anemia develops in chronic renal failure. Neutrophil leukocytosis occurs in bacterial infections of the urinary tract. Platelet function is deranged in chronic renal failure.
Biochemical tests: Investigations of the blood and urine are necessary in assessing the renal function. These tests also help in determining selectively the functions of the different parts of the nephron.
Blood Urea and Blood Urea Nitrogen (BUN): Normal blood urea is 30-40 mg/dl and BUN is 15-20mg/dl. The value of blood urea or BUN give an approximate estimate of the glomerular filtration. In addition to changes in GFR, several other factors like the state of hydration, urine flow rate and protein intake alter the serum levels of BU and BUN. These parameters, therefore are less valuable indices of glomerular filtration when compared to levels of serum creatinine.
Serum Creatinine: The normal value is 0.8-1.5mg/dl. Serum creatinine level depends mostly on the glomerular filtration rate. Creatinine is completely filtered by the glomerulus and it is not further modified during its passage down the tubules. Creatinine clearance is a reliable index of glomerular filtration rate. Normal creatinine clearance is 115+15ml/min. When the serum creatinine level is double the normal, it indicates that the clearance has fallen by 50%
Serum electrolytes: Estimation of serum electrolytes, plasma bicarbonate and pH helps to assess renal function. Serum cholesterol and lipids are elevated in some types of nephrotic syndrome and chronic renal failure.
Uric acid: Hyperuricemia may be the result of renal failure. On the contrary, a high serum uric acid level per se, irrespective of the cause, can produce renal damage. In renal failure caused by hyperuricemia, the excretion of uric acid (estimate in a 24 hour urine sample) exceeds that of creatinine.
Serum calcium levels are low in chronic renal failure. Secondary hyperparathyroidism may develop and this may result in elevation of serum calcium levels and secondary bone changes. Serum inorganic phosphorus levels are increased in acute and chronic renal failure.
Kidney Stones On X-ray
Plain X-ray of the abdomen taken after suitable preparation gives a good picture of the kidney. Abnormalities of size and presence of calculi or calcification can be seen. Normally, the two kidneys do not differ more than 2 cm in length. If the difference is greater, generally the smaller kidney tends to be abnormal. Renal function and anatomy of the collecting system can be assessed by contrast radiography [viz. intravenous urography (IVU)]. Modifications of the conventional intravenous urogram are rapid sequence IVU and high dose infusions IVU and these are done depending on the specific indications. Retrograde pyelography is the procedure by which the ureter is catheterized and the pelvicalyceal system is visualized by contrast readigraphy. Cystourethrography helps in studying the bladder, urethra and vesicoureteric junction. Micturationg cystogram i.e. picture taken while the patient passes urine after introducing radiopaque contrast into the bladder, helps in establishing the presence of vesicoureteric reflux. Aortography performed by injecting dye into the aorta, brings out the renal arteries and the renal vascular pattern. Selective angiography can be done after catheterizing the renal arteries. Renal venograms can be obtained by injecting the dye into the renal veins.
© 2014 Funom Theophilus Makama