One morning, Anne, a 25-year-old woman, noticed some discomfort on urination. Over the next few hours, her discomfort intensified and she felt a burning sensation. She had to urinate often and suddenly, but each time she passed very little urine. Her symptoms worsened during the day. The next morning, she had a fever of 101?F. She felt nauseated and noticed pain on her right side. She called her doctor.
Her physician recorded her history: fever, dysuria (painful urination), urinary frequency, and urinary urgency. When he examined her, she still had a fever and appeared quite ill. He noted tenderness when he pressed on the part of the abdomen overlying the bladder. When he tapped on the right side of her back near her kidney, she winced in pain. A urine specimen showed large numbers of bacteria and leukocytes, and the leukocytes were clumped together in thread-like masses called casts. The rest of the sample was sent to a microbiology lab for culture.
Her physician made a preliminary diagnosis of urinary tract infection (UTI), possibly a kidney infection. The lab reported that Anne’s urine sample grew a culture of Escherichia coli, with more than 100,000 bacterial cells per milliliter of urine. He prescribed antibiotics, fluids, and rest. Fortunately, the strain of #12: Title" was sensitive to the antibiotic prescribed. Seventy-two hours later, Anne felt and looked much better. Her temperature was now normal and her urinary symptoms had greatly improved. Her physician asked for another urine specimen. It contained a few white blood cells but no bacteria. Anne was told to continue taking the medication for 10 days and to return once more. Anne recovered fully during the course of therapy
1. Explain the role of the nephron in excretory system biochemistry.
2. Why is it important to differentiate between a bladder infection and a kidney infection? What is the function of the kidneys compared to the bladder?
3. Is urine normally sterile? Are bacteria, leukocytes and "casts" normal in a urine sample? What is their diagnostic significance?
4. The thread-like appearance and microscopic size of casts is suggestive of where they are formed. What part of the urinary tract has a shape which could mold such structures?
5. Routine urinalysis also includes dipstick and microscopic tests for several other abnormal components, including glucose, ketones, bilirubin, protein, nitrates, and red blood cells. How does each of these appear in the urine? What is the diagnostic significance of each of these?
*Adapted from: Human Physiology-from cells to systems by Lauralee Sherwood
Thomson/Brooks-Cole Publ. 5th edition 2004