Lower urinary tract infection: clinical approach

Lower urinary tract infections, often referred to as lower UTIs, typically involve the bladder and urethra, known as cystitis and urethritis, respectively. These infections are predominantly caused by bacteria that are usually part of the normal gastrointestinal flora, particularly gram-negative rods like E. coli, as well as Klebsiella pneumoniae and Proteus mirabilis. Lower UTIs may be categorized based on the setting and specific patient risk factors into uncomplicated, complicated, catheter-associated UTI (CAUTI), and UTI during pregnancy.

When a patient shows signs and symptoms indicative of a lower UTI, an initial ABCDE assessment is crucial to determine their stability. In cases where the patient is unstable, immediate steps should be taken to stabilize the airway, breathing, and circulation, which may include intubation, providing supplemental oxygen, securing IV access, and monitoring vital signs prior to further evaluation.

For stable patients, the focus shifts to a detailed history and physical examination, coupled with specific laboratory tests such as a urinalysis and urine culture. Symptoms to inquire about include dysuria, urinary frequency, urgency, and potentially hematuria, while a physical examination might reveal suprapubic tenderness. The urinalysis typically shows positive results for nitrites and leukocyte esterase, indicating pyuria or the presence of white blood cells, and possibly red blood cells.

A key clinical insight to remember is distinguishing between painful and painless hematuria. Painful hematuria often points to conditions like infection or nephrolithiasis, whereas painless hematuria could suggest more serious underlying issues such as renal malignancies, polycystic kidney disease, or autoimmune conditions like IgA nephropathy, which could all underpin a lower UTI diagnosis.

In healthy, pre-menopausal biologically female patients without systemic symptoms such as fever or chills, and no vaginal discharge, an uncomplicated lower UTI is typically suspected. Empiric antibiotic treatment should commence with agents effective against common gastrointestinal flora, such as nitrofurantoin, trimethoprim-sulfamethoxazole (TMP-SMX), or fosfomycin. Confirmation of the diagnosis follows if the urine culture shows a growth of over 100,000 colony-forming units per milliliter, which then guides the tailoring of antibiotics based on culture specifics.

It’s particularly notable that uncomplicated lower UTIs frequently occur in biologically female individuals due to the anatomical proximity of the urethra to the rectum. Conversely, biological males, due to their anatomical differences, are less prone to UTIs and are thus always considered to have complicated lower UTIs.

Additionally, UTIs in biological male individuals may resemble prostatitis, which can be differentiated by symptoms such as pelvic, perineal, or penile pain, a slow urine stream, and systemic symptoms like fever. A digital rectal exam should be conducted to assess for prostatic hypertrophy and labs ordered to evaluate prostate-specific antigen (PSA) levels.

Moving forward, complicated lower UTIs encompass those occurring in biological males, the elderly, immunocompromised individuals, renal transplant recipients, or those associated with systemic symptoms like fever and chills, or stemming from urinary obstruction, instrumentation, and catheter use. These cases often involve resistant organisms, necessitating the initiation of broad-spectrum antibiotics such as fluoroquinolones, TMP-SMX, or third-generation cephalosporins. Blood cultures should also be taken to exclude bacteremia. A confirmed diagnosis of complicated lower UTI follows the return of positive urine and possibly blood cultures, with subsequent antibiotic adjustment based on these culture results.

When a pregnant patient presents with urinary symptoms, it’s critical to suspect a UTI during pregnancy without waiting for urine culture results, given the risk that such an infection poses to both perinatal and neonatal health. Immediate commencement of empiric antibiotic therapy with agents like ampicillin or a cephalosporin is recommended, while avoiding medications such as trimethoprim-sulfamethoxazole (TMP-SMX) and fluoroquinolones that may harm the fetus. A positive urine culture will confirm the diagnosis of UTI in pregnancy, allowing for antibiotics to be tailored according to the culture results.

Here's another vital point! The presence of bacteria in urine without any urinary symptoms is known as asymptomatic bacteriuria. While not a traditional UTI, it's essential to treat this condition with antibiotics in certain populations at risk, such as pregnant patients or those undergoing genitourinary procedures, to prevent complications like pyelonephritis, preterm labor, or neonatal infections.

Now, regarding catheter-associated UTI, or CAUTI, this condition arises in the context of indwelling urinary catheters. If a patient with an indwelling urinary catheter exhibits UTI symptoms and systemic symptoms such as fever, CAUTI should be suspected. Initiate empiric antibiotic therapy promptly, and ensure to remove or replace the catheter while awaiting urine culture results. A negative urine culture suggests considering alternative diagnoses, but a positive culture confirms CAUTI, requiring tailoring of antibiotic therapy based on the culture findings. If yeast is grown in the culture, adding antifungal treatment should also be considered.

To sum it all up succinctly:

Lower UTIs generally involve infections of the urinary bladder and urethra, known as cystitis and urethritis respectively. When a lower UTI is suspected, an initial ABCDE assessment is crucial to determine the patient’s stability. If the patient is unstable, prioritize stabilizing their airway, breathing, and circulation. For stable patients, assess symptoms such as dysuria, frequency, and urgency, and signs like suprapubic tenderness. Perform a urinalysis that should ideally show positive results for nitrites and leukocyte esterase, indicating the presence of pyuria and hematuria.

For a healthy premenopausal female with no systemic symptoms, an uncomplicated lower UTI is likely. Start empiric antibiotic therapy and adjust based on urine culture results.

Consider a complicated UTI in cases involving biological males, as well as elderly, immunocompromised, and renal transplant patients, or in patients with systemic symptoms such as fever and chills, or those resulting from urinary obstruction, instrumentation, and urinary catheters. Begin with blood cultures to exclude bacteremia and start empiric antibiotics. Confirm the diagnosis of a complicated UTI through positive urine cultures, with or without positive blood cultures, and then tailor antibiotic treatment accordingly.

Asymptomatic bacteriuria does not generally require treatment unless the patient is pregnant or undergoing a genitourinary procedure, in which case, treat empirically with antibiotics to prevent potential complications.

Lastly, for patients with an indwelling urinary catheter exhibiting symptoms of a UTI, suspect CAUTI. Initiate treatment with empiric antibiotics and adjust based on the outcomes of the urine culture results. This comprehensive approach ensures effective management of UTIs across different patient scenarios.

Ref:

"Practice Guideline for the Management of Asymptomatic Bacteriuria: 2019 " Update by the Infectious Diseases Society of America. OUP Academic.

"International Clinical Practice Guidelines for the Treatment of Acute Uncomplicated Cystitis and Pyelonephritis in Women: A 2010 Update by the Infectious Diseases Society of America and the European Society for Microbiology and Infectious Diseases. " OUP Academic. ((2011, March 1))

"Recurrent uncomplicated urinary tract infection in women: AUA/CUA/SUFU guideline. " American Urological Association Journals. (2019)

"Medical Student Curriculum: Adult UTI - American Urological Association. " American Urological Association. (2020)

"Harrison's: Principles of Internal Medicine. " United States: McGraw-Hill Education. (2018)

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