Urinary tract infections: Pathology review

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Urinary tract infections: Pathology review



Urinary tract infections: Pathology review

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A 23-year-old woman presents to the primary care clinic due to a burning sensation with urination. The symptoms started 3 days ago and now cause the patient to wake up multiple times at night to urinate. Past medical history is unremarkable. The patient is sexually active with their spouse. Physical examination is unremarkable and vital signs are within normal limits. Urinalysis is positive for leukocytes and leukocyte esterase. Urine culture reveals growth of Gram-positive cocci. Which of the following is a feature of the causative organism most likely responsible for this patient’s condition?  


Two people came to the Nephrology ward.

The first one is 25 year old Carmen who recently returned from her honeymoon and now complains of suprapubic pain, dysuria and urinary frequency.

The other one is 35 year old Pamela who has had dysuria, fever, nausea and flank pain for the past 2 days.

On physical exam, she has costovertebral angle tenderness.

CBC and urinalysis were done for both people.

They showed that Carmen had a normal white blood cell count, but on the dipstick test, leukocyte esterase and nitrites were both positive.

For Pamela, the white blood count was high, the dipstick test showed positive leukocyte esterase and nitrites, and on microscopy, there’s white blood cell casts in the urine.

Both Pamela and Carmen have urinary tract infections, or UTIs.

This includes the lower portion of the tract like the bladder and urethra, and the upper portion of the tract like the kidneys and ureters.

UTIs are almost always caused by an ascending infection, where bacteria moves from the rectal area to the urethra and then migrate up the urethra and into the bladder.

Normally, bacteria would be washed away with urination, but in some cases, like with E. Coli, that doesn’t happen.

Instead, E. Coli uses little thread-like extensions called fimbriae to bind the uroepithelial cells and colonize the bladder mucosa, causing cystitis.

From the bladder, the infection can go up the ureter and into the kidney, where they attract neutrophils into the renal interstitium, causing pyelonephritis.


Urinary tract infections (UTIs) are common bacterial infections that can occur in any part of the urinary tract, including the kidneys, bladder, ureters, and urethra. They are most commonly caused by bacteria, such as E.coli, Klebsiella pneumoniae, Proteus mirabilis, and Staphylococcus saprophyticus.

Symptoms include pain or burning sensation when urinating, frequent urge to urinate, cloudy or strong-smelling urine, pain or pressure in the lower abdomen or back, and in more severe cases, fever or chills.

Risk factors for UTIs include female gender, sex, diabetes mellitus, indwelling catheters, pregnancy, and kidney stones. Complications of untreated or recurrent UTIs can include cystitis, pyelonephritis, and sepsis. Treatment typically involves a course of antibiotics and plenty of fluids to help flush out the bacteria.


  1. "Robbins Basic Pathology" Elsevier (2017)
  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Practical Renal Pathology, A Diagnostic Approach E-Book" Elsevier Health Sciences (2012)
  4. "Diagnosis and management of urinary infections in older people" Clinical Medicine (2011)
  5. "Urinary tract infections in women" European Journal of Obstetrics & Gynecology and Reproductive Biology (2011)
  6. "Uncomplicated Urinary Tract Infection in Adults Including Uncomplicated Pyelonephritis" Urologic Clinics of North America (2008)
  7. "Risk Factors Associated with Acute Pyelonephritis in Healthy Women" Annals of Internal Medicine (2005)
  8. "Diagnosis and Management of Acute Ureterolithiasis" American Journal of Roentgenology (2000)

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