Final answer:
A BUN level > 100 after surgery may indicate serious dehydration due to vomiting or diarrhea, leading to decreased kidney function and a potential condition of pre-renal uremia. Ulcerative colitis can also elevate BUN due to electrolyte loss.
Step-by-step explanation:
When a patient has a post-surgical blood urea nitrogen (BUN) level greater than 100, several complications could arise, signaling possible issues with kidney function. Some conditions that may lead to an elevation in BUN levels include dehydration due to vomiting, which may be associated with conditions such as pyloric obstruction or chronic intestinal obstruction, and can result in hemoconcentration and reduced blood pressure, thus affecting the glomerular filtration rate (GFR). In addition, diarrhea may cause dehydration and a subsequent increase in BUN levels, pointing to potential uremia. Another concern could be ulcerative colitis, which can result in the loss of chloride ions (Cl-) and contribute to an elevated BUN level compounded by pre-renal uremia - a condition that reflects compromised renal blood flow or function before the kidneys experiencing direct damage or disorder.