Pathophysiology of lower and upper urinary tract infections

Urinary tract infection (UTIs) refers to urinary tract symptomatic bacterial infection. As mentioned in the lesson, Escherichia coli is the most common infecting microorganism with Staphylococcus saprophyticus as the second most common (Huether & McCance, 2015, p. 753). While other organisms like fungi or viruses can infect the urinary tract, bacterial infections are most common. The lower UTI is called cystitis and affects the bladder. The upper UTI is called acute pyelonephritis and affects the kidney. Although these are the main areas for both upper and lower UTI the symptomatic bacterial infection can extend past those anatomical areas.
For lower UTIs, the onset can be sudden, with typical urgency, burning, and frequency of urination. There is often painful voiding of minor volumes of urine. Lower back pain is a common symptom. The urine may appear turbid and potential development of a low-grade fever (Huether & McCance, 2015). The symptoms for acute pyelonephritis are roughly the same as cystitis with patients often citing (33%) dysuria as a symptom. Unlike cystitis however, symptoms may include flank pain, vomiting, nausea, and chills. Patients may experience an enlarged kidney. These are clear differences between UITs in these regions. That is due to the anatomy. As the kidney and bladder serve different functions.
Women are more prone to get urinary tract infections than males and that is due to intercourse. There is a term called ‘honeymoon cystitis’ that describes a UTI after sexual intercourse. This means that gender is an important patient factor when determining infection and diagnosis. Women are more likely to get a UTI due to the short nature of their urethra and proximity it has to the vagina and anus. This is important to consider when diagnosing. Another important patient factor is age.
Age means potentially poor diet, higher incidence of chronic illness among other things like urinary incontinence, and hospital stays. Hospital acquired urinary tract infections (HAUTI) are common for nosocomial infections and can be fatal for older people. “From 162,503 patient admissions, 1.73% [95% confidence interval (CI): 1.67–1.80] of admitted patients acquired a HAUTI” (Mitchell, Ferguson, Anderson, Sear, & Barnett, 2016, p. 92). Older patients are often hospitalized and more likely to acquire UTIs thanks to prolonged catheter use.
Combine the two and there is a higher incidence of UTIs in older women. Some of this is due to urinary incontinence and urinary retention. “Risk factors for recurrent symptomatic UTI include diabetes, functional disability, recent sexual intercourse, prior history of urogynecologic surgery, urinary retention, and urinary incontinence. Testing for UTI is easily performed in the clinic using dipstick tests” (Mody & Juthani-Mehta, 2014, p. 844). These are things to look for in diagnosis.
As described earlier, the lower UTI generally affects the bladder with problems in urinating and urinating frequently and in small volumes. The upper UTI generally involves the kidneys and may lead to flank pain and potential enlargement of kidney. Both generally display through the urgency, pain, and frequency of urination. However, one may require more urgency to treat as upper UTIs may lead to kidney infections. Both kinds of infections require antibiotics and depending on the severity of an upper UTI may require antibiotics through IV.
Overall there are many similarities in symptoms regarding UTIs. The key differences lie in the severity and the gradual progression of infection. Upper UTIs can be more serious and require IV treatment whereas bladder infections are less severe and often cured through oral antibiotics.
References
Huether, S. E., & McCance, K. L. (2015). Understanding Pathophysiology - E-Book (6th ed.). Elsevier Health Sciences.
Mitchell, B., Ferguson, J., Anderson, M., Sear, J., & Barnett, A. (2016). Length of stay and mortality associated with healthcare-associated urinary tract infections: a multi-state model. Journal of Hospital Infection, 93(1), 92-99. doi:10.1016/j.jhin.2016.01.012
Mody, L., & Juthani-Mehta, M. (2014). Urinary Tract Infections in Older Women. JAMA, 311(8), 844. doi:10.1001/jama.2014.303