The following clinical vignette illustrates integration of knowledge across subject areas. The more knowledge you have in multiple subject areas, the easier questions become. If you have studied cases in problem-based, team-based, or case-based learning curricula, you have probably seen a similar case, or at least you can extrapolate from a similar case.
A _____-year-old previously healthy ______ has noted that his thirst and appetite have increased over the past 2 weeks, but he has lost 5 kg. He is urinating more frequently. On physical examination there are no abnormal findings. Urine dipstick analysis shows sp gr 1.011, pH 6, glucose 4+, ketones 4+, no blood, no protein, and no urobilinogen. Urine microscopic analysis shows a few oxalate crystals but no RBCs or WBCs. Laboratory findings on serum show creatinine 2.0 mg/dL and glucose 500 mg/dL Which of the following pathologic abnormalities most likely led to his disease?
A. Chronic pyelonephritis
B. Decreased islet cell mass
C. Increased serum globulin
D. Nodular glomerulosclerosis
E. Prostatic hyperplasia
If the student recognizes polyphagia, polydipsia, and polyuria in the stem of this question, then diabetes mellitus is present. Add findings of ketoacidosis and it is type 1 diabetes mellitus. Then, the next step is determining the pathogenesis, which is loss of beta cells in the islets of Langerhans. This question integrates across organ systems (renal, endocrine) and across disciplines (physiology, pathology). The additional clue of onset in the first two decades of life would serve to help focus the student into thinking about DM type 1, but is not needed for diagnosis here. Try to match information in the stem to prior cases you have studied. That is exactly what an expert does.
However, don't get caught in the trap of similarity, without recognizing contextual change. The case may be similar, but not exactly the same, as one you studied. If the ketoacidosis is removed from the above vignette stem, or you fail to recognize it, then type 2 diabetes mellitus is a possibility.
Don't confuse causes and consequences of disease. The lead in statement above asks for a cause, not a consequence. A long-term complication of diabetes mellitus is nodular glomerulosclerosis, and persons with diabetes mellitus are at increased risk for pyelonephritis, but that is not what the question is asking.