Final answer:
Elevated Blood Urea Nitrogen (BUN) indicates uremia, which can be a result of kidney disorders. There are three types: pre-renal, renal, and post-renal uremia, with causes ranging from dehydration to urinary tract obstructions such as kidney stones.
Step-by-step explanation:
Patients with elevated Blood Urea Nitrogen (BUN) are said to have uremia. BUN is an estimate of urea in the blood and serves as an indicator of kidney function. A BUN level above normal can signal various types of uremia—pre-renal, renal, or post-renal causes.
Renal uremia refers to an increase in blood urea nitrogen levels above 300 mg/dl due to kidney disorders. In pre-renal uremia, factors such as dehydration or hypovolemia can lead to hemoconcentration and low blood pressure, reducing the glomerular filtration rate and resulting in elevated BUN levels. Conditions like diarrhea and vomiting can also lead to pre-renal uremia. On the other hand, post-renal uremia may occur due to urinary tract obstructions, like urolithiasis (kidney stones), which can impede the excretion of urine and lead to increased BUN.