Porth's Essentials of Pathophysiology, 4e

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Kidney and Urinary Tract Function

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tissues into the bladder. The most common pathogen is Escherichia coli , followed by Klebsiella and Proteus species. In uncircumcised boys, the bacterial pathogens arise from the flora beneath the prepuce. In girls, UTIs often occur at the onset of toilet training because of uri- nation dysfunction that occurs at that age. 49 The child is trying to retain urine to stay dry, yet the bladder may produce uninhibited contractions, forcing urine out. The result may be high-pressure, turbulent urine flow or incomplete bladder emptying, both of which predispose to bacteriuria. Similar problems can occur in school- age children who refuse to use the school bathroom. 49 Constipation may increase the risk of UTI recurrence in children with VUR by compressing the bladder and bladder neck, resulting in increased bladder storage pressure and incomplete bladder emptying. 50 Unlike adults, children frequently do not present with the typical signs of a UTI. 47–51 Many neonates with UTIs have bacteremia and may show signs and symptoms of septicemia, including fever, hypothermia, apneic spells, poor skin perfusion, abdominal distention, diarrhea, vomiting, lethargy, and irritability. Older infants may present with feeding problems, failure to thrive, diarrhea, vomiting, fever, and foul-smelling urine. Toddlers often present with abdominal pain, vomiting, diarrhea, abnor- mal voiding patterns, foul-smelling urine, fever, and poor growth. In older children with lower UTIs, the classic features—enuresis, frequency, dysuria, and suprapubic discomfort—are more common. Fever is a common sign of UTI in children, and the possibility of UTI should be considered in any child with unexplained fever. Diagnosis is based on a careful history of voiding patterns and symptomatology; physical examination to determine fever, hypertension, abdominal or suprapubic tenderness, and other manifestations of UTI; and uri- nalysis to determine bacteriuria, pyuria, proteinuria, and hematuria. A positive urine culture that is obtained cor- rectly is essential for the diagnosis. 47–51 Additional diag- nostic methods may be needed to determine the cause of the disorder. Childrenwith a relatively uncomplicated first UTI may turn out to have significant reflux. Therefore, even a single documented UTI in a child requires careful diagnosis. Urinary symptoms in the absence of bacteri- uria suggest vaginitis, urethritis, sexual molestation, the use of irritating bubble baths, pinworms, or viral cystitis. In adolescent girls, a history of dysuria, and vaginal dis- charge make vaginitis or vulvitis a consideration. 49 The approach to treatment is based on the clinical severity of the infection, the site of infection (i.e., lower versus upper urinary tract), the risk for sepsis, and the presence of structural abnormalities. The immediate treatment of infants and young children is essential. Most infants with symptomatic UTIs and many children with clinical evidence of acute upper UTIs require hospi- talization, rehydration, and intravenous antibiotic ther- apy. 50,51 Follow-up is essential for children with febrile UTIs to ensure resolution of the infection. Follow-up urine cultures often are done at the end of treatment. Imaging studies often are recommended for children after their first UTI to detect renal scarring, vesicoure- teral reflux, or other abnormalities.

UrinaryTract Infections in the Elderly Urinary tract infections are relatively common in elderly persons. 43,52,53 They are the second most common form of infection, after respiratory tract infections, among otherwise healthy community-dwelling elderly. They are particularly prevalent in elderly persons living in nurs- ing homes or extended care facilities. 52 Most of these infections follow invasion of the uri- nary tract by the ascending route. Several factors pre- dispose elderly persons to UTIs, including underlying genitourinary abnormalities, immobility resulting in poor bladder emptying, diminished bactericidal proper- ties of the urine, and constipation. Prostatic hyperplasia with bladder outflow obstruction is the most important contributing factor in older men, while alteration in the bacterial flora of the vagina is the most important con- tributing factor in older women. Added to these risks are other health problems that necessitate catheteriza- tion or instrumentation of the urinary tract. Elderly persons with bacteriuria have varying symp- toms, ranging from the absence of symptoms to the presence of typical UTI symptoms. Even when symp- toms of lower UTIs are present, they may be difficult to interpret because elderly persons without UTIs com- monly experience urgency, frequency, and incontinence. Alternatively, elderly persons may have vague symptoms such as anorexia, fatigue, weakness, or change in mental status. Even with more serious upper UTIs (e.g., pyelo- nephritis), the classic signs of infection such as fever, chills, flank pain, and tenderness may be altered or absent. Sometimes, no symptoms occur until the infec- tion is far advanced. Interstitial cystitis or painful bladder syndrome is a chronic, often debilitating, condition that is character- ized by urinary frequency, urgency, and severe suprapu- bic pain. 54–56 Unlike bladder inflammation caused by a bacterial infection, the condition occurs in the absence of other pathology. Although previously reported to be a disorder of middle-aged women, it is now known that the condition affects both men and women of all ages. Although the pathophysiology of interstitial cystitis/ painful bladder syndrome is incompletely understood, it is thought to involve permeability changes of the uro- thelium, along with mast cell activation and neurogenic inflammation. Damage to the protective mucosal lining leads to impaired urothelial cell-barrier function, allowing urinary solutes to penetrate the epithelium and activate sensory nerve endings, leading to pain and inflammation. At present there are no definitive diagnostic tests for interstitial cystitis/painful bladder syndrome. Diagnostic steps involve ruling out other diseases and overlap- ping syndromes. Although not universally accepted, the potassium sensitivity test is widely used to aid in the diagnosis. The test involves the instillation of a Interstitial Cystitis/Painful Bladder Syndrome