KIDNEY INFECTIONS and SEPSIS

1. KIDNEY INFECTIONSand SEPSIS

2. acute onset of fever, chills, and flank pain are usually indicative of renal infection • significant renal infection may be associated with an insidious onset of non-specific local or systemic symptoms, or it may be entirely asymptomatic • Acute or chronic pyelonephritis may transiently or permanently alter renal function • Non obstructive pyelonephritis is no longer recognized as a major cause of renal failure • pyelonephritis, when associated with urinary tract obstruction or granulomatous renal infection, may lead rapidly to significant inflammatory complications, renal failure, or even death

3. bacterial infection of the kidney, such as pyelonephritis, was the most common cause of interstitial renal inflammation and subsequent development of serious renal disease • interstitial renal inflammation is associated with immunologic reactions, congenital lesions, or papillary damage in the absence of bacterial infection and that bacterial infection is often a secondary event

4. Pathology • kidney may be edematous • Multiple focal areas of suppuration on the surface of the kidney • Focal suppurative destruction of glomeruli and tubules • Acute ascending pyelonephritis is characterized by linear bands of inflammation extending from the medulla to the renal capsule • Wedge-shaped area of acute interstitial inflammation with the apex of the wedge in the renal medulla • Polymorphonuclear leukocytes or a predominantly lymphocytic and plasma cell response are seen

5. Acute Pyelonephritis • Inflammation of the kidney and renal pelvis • The diagnosis is clinical • Risk factors • VUR/ stone/ urinary tract obstruction/ spinal cord injury/ DM/ congenital malformation/ pregnancy/ indwelling catheters

6. Clinical Presentation • Clinical spectrum ranges from gram-negative sepsis to cystitis with mild flank pain • abrupt onset of chills, fever (100° F or greater), and unilateral or bilateral flank or costovertebral angle pain and/or tenderness • dysuria, increased urinary frequency, and urgency. • some authors regard loin pain and fever in combination with significant bacteriuria as diagnostic of acute pyelonephritis • large study of 201 women and 12 men with recurrent UTIs, showed that fever and flank pain are no more diagnostic of pyelonephritis than they are of cystitis • Of patients with flank pain and/or fever, over 50% had lower tract bacteriuria

7. Physical Examination • Tenderness to deep palpation in the costovertebral angle • Acute pyelonephritis may also simulate gastrointestinal tract abnormalities with abdominal pain, nausea, vomiting, and diarrhoea • Asymptomatic progression of acute pyelonephritis to chronic pyelonephritis, particularly in compromised hosts

8. Laboratory Diagnosis • Leukocytosis with predominance of neutrophils • Urinalysis usually reveals numerous WBCs, often in clumps, and bacterial rods or chains of cocci • The presence of large amounts of granular or leukocyte casts in the urinary sediment is suggestive of acute pyelonephritis • Blood cultures may be positive

9. Bacteriology • Urine cultures are positive, but about 20% of patients have urine cultures with fewer than 105 cfu/mL and, therefore, negative results on Gram staining of the urine • E. coli, which constitutes a unique subgroup that • possesses special virulence factors, accounts for 80% of cases • If vesicoureteral reflux is absent, a patient bearing the P blood group phenotype • may have special susceptibility to recurrent pyelonephritis caused by E. coli that have P pili and bind to the P blood group antigen receptors

10. More resistant species, such as Proteus, Klebsiella, Pseudomonas, Serratia, Enterobacter, or Citrobacter should be suspected in patients who have • recurrent UTIs • are hospitalized, or • have indwelling catheters, as well as in those who required recent urinary tract instrumentation • Blood cultures are positive in about 25% of cases of uncomplicated pyelonephritis in women

11. Ultrasound of the right kidney demonstrates renal enlargement, hypoechoic parenchyma, and compressed central collecting complex

12. Radiologic Findings • Renal Ultrasonography and Computed Tomography • Commonly used to evaluate patients initially for complicated UTIs or factors or to re evaluate patients who do not respond after 72 hours of therapy • Renal enlargement, hypo echoic or attenuated parenchyma, and a compressed collecting system • May delineate focal bacterial nephritis and obstruction

13. Pathology • Capsule strips easily, and suppuration may soften areas of parenchyma. • Usually small, yellow-white cortical abscesses mixed with parenchymal hyperaemia • Focal, patchy infiltrate of neutrophils • Early in the inflammatory process, this infiltrate is limited to the interstitium, but, later, linear bands of inflammation extend from the papillae to the cortex in a wedge-shaped manner

14. Differential Diagnosis • Acute appendicitis, diverticulitis, and pancreatitis can cause a similar degree of pain, but the location of the pain often is different.

15. Initial Management • Infection in patients with acute pyelonephritis can be subdivided into • (1) uncomplicated infection that does not warrant hospitalization, • (2) uncomplicated infection in patients with normal urinary tracts who are ill enough to warrant hospitalization for parenteral therapy, and • (3) complicated infection associated with hospitalization, catheterization, urologic surgery, or urinary tract abnormalities • Critical to determine whether the patient has an uncomplicated or complicated UTI because significant abnormalities have been found in 16% of patients with acute pyelonephritis

16. If there is any reason to suspect a problem or if the patient will not have reasonable access to imaging if there should be no change in condition, we prefer renal ultrasound to rule out stones or obstruction • Patients with known or suspected complicated pyelonephritis, • CT provides excellent assessment of the status of the urinary tract and the severity and extent of the infection. • Hospitalization, initially with complete bed rest, intravenous fluids, and antipyretics • Patients with less severe disease may be managed as outpatients • Upper tract obstruction, if suspected, should be ruled out by ultrasonography or CT.

17. An obstructed kidney has difficulty concentrating and excreting antimicrobial agents • obstruction in effect creates a potential abscess, pyonephrosis • Any substantial obstruction must be relieved expediently by the safest and simplest means. • Until the results of the culture and susceptibilities are available, • broad-spectrum antimicrobial therapy should be instituted • For patients who will be managed as outpatients, • single-drug oral therapy with a fluoroquinolone is more effective than TMP-SMX for patients with domiciliary infections

18. Ambulatory patients should be treated with • a fluoroquinolone for 7 days • Fluoroquinolone therapy is associated with greater bacteriologic and clinical cure rates than 14-day TMP-SMX therapy • Patients with complicated pyelonephritis and positive blood cultures • should be treated for 7 days with parenteral therapy. • Radiologic investigation is indicated to attempt to • identify unsuspected obstructive uropathy, urolithiasis, or underlying anatomic abnormalities that may have predisposed the patient to infection, • prevented a rapid therapeutic response, or caused complications of the infectious process, such as renal or perinephric abscess

20. Follow-Up • Repeat urine cultures should be performed on the fifth to the seventh day of therapy and 10 to 14 days and 4 to 6 weeks after discontinuing antimicrobial therapy to ensure that the urinary tract remains free of infections. • Between 10% and 30% of individuals with acute pyelonephritis relapse after a 14-day course of therapy • Patients who relapse usually are cured by a second 14-day course of therapy, but occasionally a 6-week course is necessary

21. Acute Focal or Multifocal Bacterial Nephritis • Same clinical feature as for APN • About half of the patients are diabetic, and sepsis is common • leukocytosis and UTI resulting from gram-negative organisms are found • more than 50% of the patients are bacteremic

22. Radiologic Findings • mass, most commonly poorly marginated and suggestive of renal abscess or tumour • mass has slightly less nephrographic density than the surrounding normal renal parenchyma (CT contrast) • Ultrasonography and CT aid in establishing the diagnosis • Enhancement with a contrast agent is necessary with CT studies because the lesion is difficult to visualize on the unenhanced study • Wedge-shaped areas of decreased enhancement are seen • Conversely, abscesses tend to have liquid centers, are usually round, and are present both before and after contrast medium enhancement

23. Contrast medium–enhanced CT scan demonstrates a wedge-shaped area of low density (arrows) in the middle portion of the left kidney

24. Management • Acute bacterial nephritis probably represents a relatively early phase of frank abscess formation • Treatment includes hydration and intravenous antimicrobial agents for at least 7 days, followed by 7 days of oral antimicrobial therapy • Failure to respond to antimicrobial therapy is an indication for appropriate studies to rule out obstructive uropathy, renal or perirenal abscess, renal carcinoma, or acute renal vein thrombosis

25. Emphysematous Pyelonephritis • Emphysematous pyelonephritis is an acute necrotizing parenchymal and perirenal infection • caused by gas-forming uropathogens • pathogenesis is poorly understood • usually occurs in diabetic patients • high tissue glucose levels provide the substrate for micro-organisms such as E. coli, which are able to produce carbon dioxide by the fermentation of sugar

26. Many patients have urinary tract obstruction associated with urinary calculi or papillary necrosis and significant renal functional impairment • Impaired host response caused by local factors, such as obstruction, or a systemic condition, such as diabetes, • allows organisms with the capability of producing carbon dioxide to use necrotic tissue as a substrate to generate gas in vivo • The overall mortality rate has been reported to be between 43% ( Freiha et al, 1979 ) and 19%

27. Clinical Presentation • Almost all patients display the classic triad of fever, vomiting, and flank pain • All of the documented cases of emphysematous pyelonephritis have occurred in adults

28. Radiologic Findings • Tissue gas that is distributed in the parenchyma may appear on abdominal radiographs as mottled gas shadows over the involved kidney • Crescentic collection of gas over the upper pole of the kidney is more distinctive • As the infection progresses, gas extends to the perinephric space and retroperitoneum

29. CT is the imaging procedure of choice in defining the extent of the emphysematous process and guiding management • An absence of fluid in CT images or the presence of streaky or mottled gas with or without bubbly and loculated gas • appears to be associated with rapid destruction of renal parenchyma and a 50% to 60% mortality rate

30. CT scan obtained after administration of contrast material shows a low-attenuation area (arrowheads) in the right kidney due to acute pyelonephritis as well as a subcapsular abscess with fluid and bubbly and loculated gas

31. Management. • Emphysematous pyelonephritis is a surgical emergency • Most patients are septic, and fluid resuscitation and broad-spectrum antimicrobial therapy are essential • If the kidney is functioning, medical therapy can be considered

32. Nephrectomy is recommended for patients who do not improve after a few days of therapy • If the affected kidney is non-functioning and not obstructed • nephrectomy should be performed because medical treatment alone is usually lethal • If a kidney is obstructed, catheter drainage must be instituted

33. Renal Abscess • Renal abscess or carbuncle is a collection of purulent material confined to the renal parenchyma • Before the antimicrobial era, 80% of renal abscesses were attributed to hematogenous seeding by staphylococci

34. Since about 1970, gram-negative organisms have been implicated in the majority of adults with renal abscesses • Hematogenous renal seeding by gram-negative organisms may occur • Association of pyelonephritis with vesicoureteral reflux is well established, the association of renal abscess with vesicoureteral reflux has been infrequently noted

35. Clinical Presentation • fever, chills, abdominal or flank pain • A thorough history may reveal a gram-positive source of infection 1 to 8 weeks before the onset of urinary tract symptoms • The infection may have occurred in any area of the body • Multiple skin carbuncles and intravenous drug abuse introduce gram-positive organisms into the bloodstream • Complicated UTIs associated with stasis, calculi, pregnancy, neurogenic bladder, and diabetes mellitus also appear to predispose the patient to abscess formation

36. Multiple skin carbuncles and intravenous drug abuse introduce gram-positive organisms into the bloodstream • Complicated UTIs associated with • stasis, calculi, pregnancy, neurogenic bladder, and • diabetes mellitus also appear to predispose the patient to abscess formation

37. Radiologic Findings • Differentiation between early renal abscesses and acute pyelonephritis can be difficult because most of the former are small • In a more chronic abscess, the predominant urographic abnormalities are those of a renal mass lesion • Ultrasonography is the quickest and least expensive method to demonstrate a renal abscess

38. An echo-free or low echodensity space-occupying lesion with increased transmission is found on the sonogram • The margins of an abscess are indistinguishable in the acute phase, but the structure contains a few echoes and the surrounding renal parenchyma is edematous • Differentiation between an abscess and a tumour is impossible in many cases • CT appears to be the diagnostic procedure of choice for renal abscesses • abscesses are characteristically well defined both before and after contrast agent enhancement

39. After several days of the onset of the infection, a thick fibrotic wall begins to form around the abscess • An echo-free or slightly echogenic mass due to the presence of necrotic debris is seen • CT of a chronic abscess shows • obliteration of adjacent tissue planes, • thickening of Gerota's fascia, a round or oval parenchymal mass of low attenuation, • and a surrounding inflammatory wall of slightly higher attenuation that forms a ring when the scan is enhanced with contrast material

40. Enhanced CT scan shows an irregular septated low-density mass (M) extensively involving the left kidney. Note thickening of perinephric fascia (arrowheads) and extensive compression of the renal collecting system

41. Management • Although the classic treatment for an abscess has been percutaneous or open incision and drainage • good evidence that the intravenous use of antimicrobial agents and careful observation of a small abscess less than 3 cm in diameter, if begun early enough in the course of the process, may obviate surgical procedures • CT- or ultrasound-guided needle aspiration may be necessary to differentiate an abscess from a hypervascular tumour. • hematogenous dissemination is suspected, the pathogenic organism most frequently is penicillin-resistant Staphylococcus, and the antimicrobial of choice therefore is a penicillinase-resistant penicillin

42. Cortical abscesses that occur in the abnormal urinary tract are associated with • more typical gram-negative pathogens and should be treated empirically with intravenous third-generation cephalosporins, antipseudomonal penicillins, or aminoglycosides • Serial examinations with ultrasonography or CT until the abscess resolves • Abscesses 3 to 5 cm in diameter and smaller abscesses in immunocompromised hosts or those that do not respond to antimicrobial therapy • should be drained percutaneously

43. Infected Hydronephrosis and Pyonephrosis • Infected hydronephrosis is bacterial infection in a hydronephrotic kidney • Pyonephrosis refers to infected hydronephrosis • associated with suppurative destruction of the parenchyma of the kidney, in which there is total or nearly total loss of renal function

44. Clinical Presentation • high fever, chills, flank pain, and tenderness • previous history of urinary tract calculi, infection, or surgery is common • Bacteriuria may not be present if the ureter is completely obstructed

45. Radiologic Findings • Ultrasonographic diagnosis of infected hydronephrosis depends on • demonstration of internal echoes within the dependent portion of a dilated pyelocalyceal system • CT is non-specific but may show thickening of the renal pelvis, stranding of the perirenal fat, and a striated nephrogram

46. Longitudinal ultrasound scan of the right kidney demonstrates echogenic central collecting complex (C) with radiating echogenic septa (arrows) and thinned hypoechoic parenchyma. Multiple dilated calyces (o) with diffuse low-level echoes are seen

47. Management • The treatment is initiated with appropriate antimicrobial drugs and drainage of the infected pelvis

48. Perinephric Abscess • Results from rupture of • an acute cortical abscess into the perinephric space or from hematogenous seeding from sites of infection • Patients with pyonephrosis, particularly when a calculus is present in the kidney, • are susceptible to perinephric abscess formation • Diabetes mellitus is present in approximately one third of patients with perinephric abscess • A perirenal hematoma can become secondarily infected by the hematogenous route or by direct extension of a primary renal infection

49. Clinical Presentation • Clinical presentation may be similar to that of pyelonephritis • More than one third of patients may be afebrile • Psoas abscess should be suspected if the patient has a limp and flexion and external rotation of the ipsilateral hip

50. CT is particularly valuable for demonstrating the primary abscess • Ultrasonography and CT can usually delineate the abscess outside Gerota's fascia.