All of the following are correct for causes of intrarenal acute kidney injury except:

A. 90-year-old female whose blood urea nitrogen (BUN) is rising: An isolated rise in BUN can indicate dehydration, gastrointestinal bleeding, or renal impairment. While BUN may increase slightly with age, a significant rise should not be dismissed as normal aging and warrants further investigation.

B. 81-year-old male whose serum creatinine level has increased sharply since his last blood work: A sharp increase in creatinine is not typical with aging and may suggest acute kidney injury or worsening chronic kidney disease. In older adults, even small creatinine changes can be significant due to reduced muscle mass.

C. 80-year-old male whose dipstick urine reveals protein is present: Proteinuria is not a normal part of aging and may indicate underlying kidney damage, hypertension, or diabetes. Even trace amounts of protein in the urine of older adults should prompt further evaluation to rule out nephropathy.

D. 78-year-old female whose GFR has been steadily declining over several years: A gradual decline in glomerular filtration rate (GFR) is expected with aging due to nephron loss and reduced renal perfusion. This change is a normal physiologic part of aging, provided there are no abrupt drops or accompanying signs of renal disease.

A. High fiber diet, laxatives, increased water intake, increased reflex for defecation: These factors promote healthy bowel movements. Fiber adds bulk to stool, water softens it, laxatives stimulate movement, and an intact defecation reflex supports regular elimination, all of which prevent constipation.

B. Decreased fiber diet, decreased water intake, decreased reflex for defecation: These are contributing factors to constipation. However, it leaves out other significant causes like medications and medical conditions that impair bowel function.

C. Increased fiber diet, increased hydration, increased reflex for defecation, medications, absence of disease processes: Fiber, hydration, absence of disease and a strong reflex help prevent constipation. However, medications like opioids and anticholinergics often cause constipation regardless of diet and hydration.

D. Decreased fiber diet, decreased hydration, decreased reflex for defecation, medications, disease processes: A low-fiber diet and poor hydration lead to hard stools. A weak defecation reflex can result from neurological decline. Medications and chronic diseases such as diabetes or hypothyroidism can slow intestinal motility.