Clin. RadioL (1975) 27, 513-519

P Y O N E P H R O S I S

IAIN WATT* and JOHN ROYLANCE

From the Department of Radiodiagnosis, United Bristol Hospitals

The clinical and radiological features of pyonephrosis are reviewed, based on a con- secutive series of 40 cases. There were 32 female and eight male patients, with a peak incidence in the 50-59 year age group. In 63 % of cases the right kidney was involved. Almost all patients complained of loin pain and 48 % had lower urinary tract symptoms. In 58 ~ of cases a renal mass was palpable. An anaemia, pyuria and elevated blood sedimentation rate were usual. Plain films of the abdomen revealed enlargement of the outline of the involved kidney in 75 ~ , ipsilateral absence of the psoas shadow in 63 % and urinary tract calculi in 60 ~. At high-dose excretion urography a nephrogram was obtained in 58 ~ of cases and a pyelogram produced in 34 %.

No single clinical or radiological entity emerged, there being an unbroken spectrum of disease ranging from infected hydronephrosis to xanthogranulomatous pyelonephritis. There is an increasing incidence of calculi, loss of the renal and psoas outlines and reduced renal function with increasing chronicity of disease. High-dose excretion uro- graphy is the investigation of choice since not only may the diagnosis be established but also the precise pathological state of the involved kidney. Further radiological investiga- tion is infrequently required.

INTRODUCTION

PYONEPHROSIS is a rare disease defined as distension of the pelvis and calyces of the kidney by pus. The clinical manifestations have altered in recent decades and most patients do not now present in an acutely ill state (Hodson and Edwards, 1970). This altera- tion may be due to the earlier use of antibiotics for urinary tract infections, and can present the radio- logist with difficulties in diagnosis. Most standard textbooks state that when pyonephrosis is present, renal function has usually been destroyed to the point where excretion urography is of no value (Paul and Juhl, 1965) and that the diagnosis is usually made by retrograde pyeloureterography (Hudson and Edwards, 1970; Emmett and Witten, 1971). No report of the appearances of pyonephro- sis has been made since the introduction of high- dose excretion urography. A consecutive series of 40 patients has been studied to examine the current ciinical, pathological and radiographic features of the disease. Findings are summarised in Table 1.

* Read to the Spring Meeting of the Faculty of Radio- logists at Exeter, and to the Urological Section of the Royal Society of Medicine in Bristol, 1974.

PATIENTS

The series comprises all the patients who pre- sented with non-tuberculous pyonephrosis to the United Bristol and Southmead General Hospitals over the past seven years. The annual incidence is of the order of 1 in 50 000 of the population. There were 32 female and 8 male patients. Their ages were between 18 and 88 years with a peak in the 50-59 year old age group.

RESULTS

P a t h o l o g y . - Thirty-two nephrectomy specimens and one partial nephrectomy specimen were avail- able for review. In nearly three-quarters the right kidney was involved (Fig. 1).

In six there were changes of acute inflammation with polymorphonuclear leucocyte infiltration and urothelial haemorrhage. Seventeen showed changes of chronic low-grade infection with lymphocyte infiltration and fibrosis. Thirteen of this group also showed advanced changes of chronic pyelonephritis, and eight had xanthogranulomatous pyelonephritis. Ten specimens showed an acute inflammatory pro- cess superimposed upon chronic changes which

513

514 C L I N I C A L R A D I O L O G Y

RIGHT 5

N U M B E R

O F

C A $ E S

I

9 19 39 4 9 79 AGE

LEFT [ ~ '

FIG. 1 Age and sex distribution of 40 patients with pyonephosis.

included xanthogranulomatous nodules in two specimens.

Predisposing factors were shown in 39 patients. These were pelvic hydronephrosis (20), calculus obstruction (12), ureteric stricture (four), transi- tional cell carcinoma of the bladder (two), and ureteric obstruction by necrotic debris from a renal cell carcinoma (one). Other possible contributory factors included previously undiagnosed diabetes mellitus (three), congestive cardiac failure (three), pregnancy (one), proctocolitis (one), and long-term steroid therapy for Still's disease (one).

Clinical Features. - The length of history prior to presentation varied from three days to 20 years. Thirty-four patients complained of loin pain, 19 of frequency and dysuria, and eight of haematuria. Fifteen patients presented with vomiting and eight with weight loss. On admission, 33 patients were pyrexial and in 12 the temperature exceeded 102°F. Loin tenderness was present in 37 patients and a palpable renal mass was present in 23.

Routine examination of the blood showed a range of haemoglobin between 7 and 16.3 g with a mean on 11.0 g. The white cell count was variable. The erythrocyte sedimentation rate was elevated in all except two patients, with a mean of 55 mm/h.

Urine findings were recorded in 39 patients. Eight patients had sterile pyuria. In 31 there was pyuria with a significant growth comprising E. eoli in 16, B. proteus in seven, Pseudomonas in one, Klebsiella in one and mixed organisms in six. Eight of the patients also had haematuria. In ten patients in whom a swab of the pus in the renal pelvis was taken at the time of operation, the organism was the same as that previously cultured from the urine.

Nephrectomy was performed in 32, nephrostomy in four, pyelolithotomy in three and partial neph- rectomy in one. Thirty-five patients recovered. Five patients died, two from carcinomatosis, and one each from septicaemia, post-operative pneu- monia and amyloidosis.

Radiological Findings

Plain films of the abdomen at the time of presen- tation were available for review in all 40 patients. A lumbar scoliosis was present concave to the side of the lesion in two patients. The renal outline on the affected side was normal in only one patient. There was enlargement of the affected kidney in 30 with localised renal enlargement in one. In seven of these patients and four others the renal outline was ill-defined. No renal outlines could be discerned in four patients. The psoas shadow was absent on the affected side in 25 patients. It was absent on both sides in one case. Calculi were present in 24 patients. There were 13 with staghorn calculi, four with rounded renal calculi, four with amorphous intrapeNic calcification (Fig. 2), three with ureteric calculi of whom two also had intrapelvic calculi. None was seen in the contralateral upper urinary tract. Gas was present in the dilated calyces of a patient with a reno-colic fistula. This patient has been reported elsewhere (Newman and Jeans, 1972).

Excretion urography was undertaken at the time of presentation in 38 patients. A nephrogram was obtained in the affected kidney in 22 patients. This was normal in two, uniform low density in seven, and sustained in two (Fig. 3). A small main renal artery was shown on bolus nephrography in one (Fig, 4). Six patients showed a soap-bubble nephrogram (Fig. 5) and four a rim nephrogram (Fig. 6A, B). A pyelogram was obtained in 13 patients. A ball pyelogram was seen in nine cases, two of which showed ill-defined filling defects due to pus (Fig. 7A). In one case an erect film revealed multiple pus-contrast medium fluid levels (Fig. 7B). In two patients a low-density pyelogram showed dilatation of the penis and ureter down to the level of calculus obstruction. In one there was a filling

Fro. 2 Chronic pyonephrosis. The kidney is enlarged and its outline ill-defined. Amorphous intra-pelvic calcification and upper

ureteric calculi are present (Mrs E.B., aged 63 years).

Fio. 3 Acute pyonephrosis. A sustained nephrogram is present at the 10 min stage of excretion urography. There is an obstruct- ing calculus in the upper ureter (Mrs M.R_, aged 24 years).

FIG. 4 Chronic pyonephrosis. A uniform low-density nephrogram and small main renal artery are shown following a bolus injection. A calculus is present in the lower pole (Miss M.R.,

aged 19 years).

FIG. 5 Acute pyonephrosis. Excretion urography demonstrates a soap-bubble nephrogram in an enlarged kidney. The psoas

shadow is preserved (Miss I.D., aged 17 years).

516 CLINICAL RADIOLOGY

FIe. 6 A. Acute on chronic pyonephrosis. A 10 min film at excre-

tion urography reveals crescents in the upper pole. A fragmented staghorn calculus and amorphous intrapelvic calcification are present. The involved kidney is enlarged but well-defined with a preserved psoas shadow (Mrs S.S., aged 50 years. Long history of chronic urinary infection treated conservatively on this occasion.)

B. Same patient two months later when acutely ill. There is now massive enlargement of the kidney. The previous crescents are no longer present and have been replaced by ill-defined soap bubbles.

FI~. 7 n. Acute on chronic pyonephrosis. A ball pyelogram is

present at the 20 rain stage of excretion urography. There are ill-defined filling defects due to pus (Mrs E_D., aged 54 years).

B. Same patient. An erect film at 45 rain reveals multiple pus/contrast medium fluid levels.

PYONEPHROSIS 517

FIG. 8 Acute on chronic pyonephrosis. A retrograde pyelogram shows dilatation of the pelvicalyceal system, ulceration of the urothelium and ill-defined filling defects due to pus (Mr J.G.,

aged 82 years).

Fro. 9 Acute pyonephrosis. A retrograde pyelogram reveals dilata- tion of the upper pole calyces and a large irregular filling

defect in the pelvis with amputation of the middle and lower calyces due to renal cell carcinoma (Mr C.B., aged 68 years).

Fro. 10 Chronic pyonephrosis. An antegrade pyelogram converted to needle nephrostomy demonstrates the classical appear- ances of primary pelvic hydronephrosis (Mrs E.H., aged

88 years).

defect in the renal pelvis due to a renal cell carcinoma and in another there was no function in the upper moiety of a duplex kidney.

The contralateral kidney was normal in 35 patients. One case each of chronic pyelonephritis, hydronephrosis and a duplex system were seen.

Retrograde pyeloreterography was attempted in eight patients. The procedure was a technical failure in two of these, in whom the Braasch bulb method was employed. The other six revealed gross dilata- tion of the pelvicalyceal system and pus was aspirated. Five demonstrated a shaggy pelvicalyceal outline with filling defects due to purulent material (Fig. 8), the sixth confirmed an irregular mass due to a renal cell carcinoma (Fig. 9).

Antegrade pyelography was performed in two cases; in both, pus was aspirated. One case revealed primary pelvic hydronephrosis (Fig. 10), the other a reno-colic fistula.

Selective renal arteriography was undertaken in four cases. In three a large kidney was demon- strated with narrow main renal arteries, sparse and

33

pruned intrarenal vessels, with some zones of rela- tively normal vascularity and irregular avaseular areas in the nephogram. One of these had a localised avascular renal mass due to a pyocalycosis second- ary to obstruction by a fragmented staghorn calculus. The fourth patient showed a largely avascular renal cell carcinoma and in common with the other three, there was free filling and displacement of periureteric and capsular vessels.

Isotope investigations were undertaken in five patients. Scintigraphy using 99Tcm was performed in two cases. Both revealed overall reduced uptake with small renal images. At urography in both cases a normal sized kidney had been demonstrated with the development of a nephrogram and pyelo- gram. Isotope renography was performed in three cases, all showing reduced peaks and delay in the third stage interpreted as being consistent with obstructive uropathy.

Ultrasound scanning was performed in only one case. This patient was pregnant and had a mass in the right upper abdomen. The ultrasound scan

518 CLINICAL RADIOLOGY

TABLE 1 COMPARISON OF THE PRINCIPAL CLINICAL AND RADIOLOGICAL FEATURES OF INFECTED HYDRONEPHROSIS, PYONEPHROSIS AND

XANTHOGRANULOMATOUS PYELONEPHRITIS

Female incidence Average age Right side involved Renal outline present Psoas shadow present Calculi present Nephrogram present Pyelogram develops Xanthogranulomatous

pyelonephritis on histology

Infected hydronephrosis

46% 46 years

50% 100% 90% 12%

100% 85%

o%

Acute pyonephrosis

83% 44years

50700 50% 50% 33% 83700 33%

o%

Acute on chronic

pyonephrosis

80% 60 years

50% 0%

30% 60% 20% 10%

20%

Chronic pyonephros~

88% 54 years

75% 35% 41% 53% 59% 47%

47%

Xanthogranu- lomatous

pyelonephritis

45% 43 years

55% 18% 18% 57% 40% 27%

100%

revealed a well-defined transonic mass and excretion urography confirmed a non-functioning upper moiety of a duplex kidney.

DISCUSSION

Pyonephrosis forms an unbroken spectrum of disease ranging without any clear distinction from infected hydronephrosis to the diffuse forms of xanthogranulomatous pyelonephritis. Accurate classification of the individual case is important if conservative therapy for acute disease is to be con- templated. Thus the diagnostic demands presented by pyonephrosis are not only to establish its pre- sence, the cause of the obstruction, the presence of complications and the state of the contralateral kidney, but also to determine the precise patho- logical state of the kidney. The clinical features are of importance in two ways. They indicate the need for radiological investigation of the kidney and when correlated with the results of these investiga- tions, may provide a full diagnosis. The patient usually presents a clinical picture which is consistent with an infection. However, the features vary greatly from those of an acute, severe toxaemia with a high swinging fever to that of general malaise with weight loss over a long period. Pain and tenderness in the loin and the finding of pyuria will suggest the presence of suppuration within the kidney. The clinical presentations broadly corre- spond with the grade of disease found histologically although several exceptions to this correlation occurred. The predilection for females and for the

right kidney is unexplained but may be related to previous pregnancies and the ovarian vein syn- drome.

The results of this series indicate that the first investigation should be high-dose excretion uro- graphy. This will usually demonstrate obstruction of the kidney with reduced function and this in association with the clinical features clinches the diagnosis. It will often reveal the cause of the obstruction. It will show whether the contralateral kidney is present and normal, a vital consideration when pyonephrosis is treated by nephrectomy. The radiological features form a spectrum from those of uncomplicated hydronephrosis (Davies et al., 1972) to those of xanthogranulomatous pyelonephritis (Gingell et al., 1973) with an increas- ing incidence of calculi, loss of renal and psoas outlines and reduced renal function with increasing chronicity of the disease (Table 1). Further in- vestigations may be of value for diagnosis and, in some instances, for treatment, although they are not often necessary and were infrequently employed in the present series. Retrograde pyelouretero- graphy demonstrates the radiological features well, and will enable pus to be aspirated to confirm the diagnosis and facilitate bacteriological assessment. The preliminary cystoscopy may be undesirable in the acutely ill patient and catheterisation of the ureter may be prevented by the obstruction. The antegrade approach can then be employed to advantage (Jeans et al., 1972), and needle nephro- stomy may be indicated for drainage and the instillation of suitable antibiotic agents (Saxton

PYONEPHROSIS 519

et al., 1972). Diagnostic ul t rasound is of use as the initial investigation when there is a relative contraindication to excretion urography as in the patient who was pregnant. I t is said to be of value in differentiating pyonephrosis f rom hydronephro- sis by the demonstrat ion of ill-defined margins to the dilated collecting systems which may contain echoes due to pus (Barnett and Morley, 1972). Angiography is of value when there is no renal function and will usually demonstrate both the features o f stretched at tenuated vessels, due to hydronephrosis, and irregular vascularised areas of inflammation. A diagnosis of pyonephrosis is thereby established. Angiography must be seriously considered in each case for the demonstrat ion of possible coexisting renal disease, especially renal cell carcinoma. Isotope studies will yield non- specific evidence of reduced renal function and will help to assess the presence and normali ty of the contralateral kidney.

C O N C L U S I O N S

1. There is an uninterrupted spectrum of disease f rom infected hydronephrosis through the various forms of pyonephrosis to xanthogranulomatous pyelonephritis.

2. High-dose excretion urography is the radio- logical investigation of choice.

3. A nephrogram is seen in more than half and a pyelogram in a third o f the patients.

4. Correlation o f the clinical and urographic features allows the state of the kidney to be accurate- ly diagnosed.

5. Fur ther radiological investigations are not often needed, but may be of value for the demon- stration o f coexistent disease and for treatment.

Acknowledgements. - The authors wish to thank Dr J. B. Penry and his colleagues who performed many of the radio- logical investigations on the Southmead Hospital group of patients. They are also grateful to Dr E. R. Davies for his helpful criticism and advice; to Messrs Hancock and Turn- bull for their photographic and artistic help; and to Miss S. Smith for secretarial assistance.

REFERENCES

BARNETT, E. & MORLEY, P. (1972). Diagnostic ultrasouna m renal disease. British Medical Bulletin, 28, 196-199.

DAVIES, P., ROYLANCE, J. • GORDON, I. R. S. (1972). Hydro- nephrosis. Clinical Radiology, 23, 312-320.

EMM~TT, J. L. & WITTEN, D. M. (1972). Clinical Urograpky, 3rd edn, Vol. 2, p. 801. W. B. Saunders Company, Philadelphia, London, Toronto.

GINGELL, J. C., ROYLANCE, J., DAVIES, E. R. & PENRY, J. B. (1973). Xanthogranulomatous Pyelonephritis. British Jour- nal~ofRadiology, 46, 99-109.

HODSON, C. J. & EDWARDS, D. (1970). Inflammatory lesions of the kidney. In ,4 Textbook of X-ray Diagnosis, 4th edn, ed. Shanks, S. C. & Kerley, P., Vol. 5, p. 365~ Lewis, London.

JEANS, W. D., PENRY, J. B. & ROYLANCE, J. (1972). Renal puncture. Clinical Radiology, 23, 298-311.

NEWMAN, J. H. & JEANS, W. D. (1972). Reno-colic fistula demonstrated by antegrade pyelography. British Journal of Urology, 44, 692-697.

PAUL, L. W. & JUt-m, J. H. (1965). The Essentials of Roentgen Interpretation, 2nd edn, p. 523. Hoeber Medical Division, Harper and Row, New York.

SAXTON, H. M., OoG, C. S. & CAMERON, J. S. (1972). Needle nephrostomy. British Medical Bulletin, 28, 210-213.