Management of idiopathic retroperitoneal fibrosis from the urologist's perspective

Overview of F18-FDG uptake patterns in retroperitoneal pathologies: imaging findings, pitfalls, and artifacts

INTRODUCTION

Retroperitoneum can be the origin of a wide variety of pathologic conditions and potential space for disease spread to other compartments of the abdomen and pelvis. Computed tomography (CT) and magnetic resonance imaging (MRI) are often the initial imaging modalities to evaluate the retroperitoneal pathologies, however given the intrinsic limitations, F18-FDG PET/CT provides additional valuable metabolic information which can change the patient management and clinical outcomes. We highlight the features of retroperitoneal pathologies on F18-FDG PET/CT and the commonly encountered imaging artifacts and pitfalls. The aim of this review is to characterize primary and secondary retroperitoneal pathologies based on their metabolic features, and correlate PET findings with anatomic imaging.

CONCLUSION

Retroperitoneal pathologies can be complex, ranging from oncologic to a spectrum of non-oncologic disorders. While crosse-sectional imaging (CT and MRI) are often the initial imaging modalities to localize and characterize pathologies, metabolic information provided by F18-FDG PET/CT can change the management and clinical outcome in many cases.

Retroperitoneal fibrosis is still underdiagnosed entity with poor prognosis

BACKGROUND

Retroperitoneal fibrosis (RPF) is a rare disease characterized by the presence of inflammatory and fibrous retroperitoneal tissue that often encircles abdominal organs including aorta and ureters. Data on the incidence of this disease are limited.

SUMMARY

The disease may be idiopathic or secondary to infections, malignancies, drugs or radiotherapy. Idiopathic form is an immune-mediated entity and a part of the broader spectrum of idiopathic diseases termed chronic periaortitis, characterized by a morphologically similar fibroinflammatory changes in aorta and surrounding tissues. Taking into account the dominant symptoms and clinical charac-teristics of patients with periaortitis, two subtypes of disease could be distinguished. Vascular subtype include patients with non-dilated aorta or with inflammatory abdominal aortic aneu-rysm, both with and without involvement of adjacent structures and with numerous risk factors for atherosclerosis. In renoureteral subtype obstructive uropathy manifesting with hydronephro-sis and acute kidney injury is predominant finding. Due to the variety of symptoms, diagnosis of RPF remains challenging, difficult and often delayed. A series of diagnostic tests should be performed, in order to confirm the diagnosis idiopathic RPF. Laboratory work-up include eval-uation of inflammatory indices and immunological studies. A biopsy and histopathological evaluation may be necessary to confirm diagnosis and differentiate the disease. Computed to-mography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET) are the modalities of choice for the diagnosis and follow-up of this disease. Management of ureteral obstruction, hydronephrosis, and aortic aneurysms often requires surgical evaluation and treatment. The pharmacological treatment of RPF has been evaluated in a few randomized trials and is mainly based on observational studies. Steroid therapy remains the gold standard of treatment. Key messages: Nowadays multidisciplinary team approach with clinical and diagnos-tic experience in both primary and secondary RPF as well as two major subtypes should be offered. Centers specialized in rare diseases with collaboration with other units and referral sys-tem yield the best possible outcomes.

[Retroperitoneal fibrosis at the Ibn Sina University Hospital of Rabat: about 18 cases]

La fibrose rétropéritonéale (FRP) est une pathologie rare caractérisée par la formation d´une plaque fibro-inflammatoire dans l´espace rétropéritonéale en avant de l´aorte abdominale, responsable d´un engainement des uretères. Le tableau clinique n´est pas spécifique et la pathologie est souvent révélée par une uropathie obstructive. Nous avons mené une étude descriptive rétrospective étendue sur 10 ans, de janvier 2006 à décembre 2016, réalisée dans les services d´urologie B et de néphrologie du Centre Hospitalier Universitaire Ibn Sina. Nous avons inclus 18 patients dans l´étude dont 11 hommes et 7 femmes, avec un âge moyen de 51,4 ans ± 11,2. Le diagnostic a été révélé par des douleurs lombaires chez 14 patients. L´insuffisance rénale obstructive était présente chez 15 de nos patients et le diagnostic de FRP a été posé par l´uroscanner. Le bilan étiologique notait des antécédents de néoplasies pour 2 patients, de pathologies inflammatoires pour 2 autres patients et une chirurgie rétropéritonéale chez un patient. On notait l´association de prises médicamenteuses chroniques chez plus de la moitié des patients. Le traitement comportait un double volet: une sonde double J systématique chez tous les patients et un traitement systémique par de la corticothérapie et des immunosuppresseurs selon le profil évolutif. Le traitement par urétérolyse a été réalisé d´emblée chez 3 patients. L´évolution a été favorable avec une nette amélioration de la fonction rénale chez 12 patients. La rechute est survenue chez 2 patients après 2 ans de suivi. L´association de signes généraux à une insuffisance rénale obstructive doit faire évoquer le diagnostic de FRP. La recherche de causes secondaires devrait être systématique, avec un accent particulier à mettre sur le syndrome d´hyper IgG4 et les pathologies néoplasiques.

[Clinical features of hydronephrosis induced by retroperitoneal fibrosis: 17 cases reports]

OBJECTIVE

To investigate the clinical features and outcome of hydronephrosis induced by retroperitoneal fibrosis (RPF), and to evaluate the effect of corticosteroid based therapy combined with surgical intervention of ureteral obstruction.

METHODS

A total of 17 RPF patients with hydronephrosis hospitalized in Peking University International Hospital from May 2016 to December 2019 were analyzed retrospectively.

RESULTS

The median age was 56 (53, 65) years, the male to female ratio was 2.4 : 1, and the disease duration was 4.00 (0.83, 8.00) months. The initial symptoms included back pain (9 cases), abdominal pain (6 cases), oliguria (2 cases) and lower limb edema (3 cases). Eight patients presented left hydronephrosis, 1 right hydronephrosis and 8 bilateral hydronephrosis. C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) were both elevated in 13 patients (76.5%, n=17). Immunoglobin (Ig) G4 increased in 5 cases (29.4%, n=17). IgG, IgE and IgA increased in 4 cases (30.8%, n=13), 4 cases (30.8%, n=13) and 1 case (7.7%, n=13), respectively. Among 12 patients who underwent biopsy, 3 patients were diagnosed with IgG4-relate disease. The level of IgG4 in the tissues varied, 6 cases expressed less than 10 per high power field (HPF) or no expression (50.0%). Only 2 cases expressed 10-30/HPF (16.7%), and 4 cases revealed more than 30/HPF (33.3%). Among the 17 patients with ureteral obstruction, no urinary drainage procedure was needed in 4 patients who had mild ureteral obstruction, whereas, ureteral stenting was carried out in the other 13 cases before drug treatment. Time was too short to evaluate the effect of urinary drainage procedures in 4 patients. For the rest, ureterolysis had to be performed in 3 cases after failed ureteral stent insertion. Successful drain removal was accomplished in all of these 9 patients and the mean time to drain removal was (6.7±3.0) months. In addition, 10 patients had complete medical records after an average follow-up time of 5 (3-13) months. Levels of ESR, CRP, IgG4, IgG, IgE, IgA were 54.0 (36.3, 98.5) mm/h, 26.8 (8.7, 53.0) mg/L, 1.34 (0.55, 3.36) g/L, 16.3 (13.0, 21.1) g/L, 40.5 (31.4, 203.0) IU/mL, 2.51 (1.82, 3.25) g/L at baseline, which all decreased predominantly after treatment. ESR, CRP, IgG4, IgG, IgE and IgA dropped by 38.5 (23.5, 54.3) mm/h (P < 0.01), 23.0 (5.5, 52.0) mg/L (P < 0.05), 0.92 (0.40, 2.85) g/L (P < 0.01), 6.5 (1.7, 9.1) g/L (P < 0.05), 23.7 (4.8, 162.0) IU/mL (P < 0.05) and 0.77 (0.32, 1.26) g/L (P < 0.05), respectively. Size of mass measured by CT/MRI imaging became smaller significantly and hydronephrosis relieved.

CONCLUSION

Onset of RPF is insidious and lack of specific initial symptoms. Corticosteroid based therapy combined with surgical intervention of relieving obstruction is effective.

Retroperitoneal Fibrosis and its Differential Diagnoses: The Role of Radiological Imaging

Background Retroperitoneal fibrosis is a rare disease with an incidence of 0–1/100 000 inhabitants per year and is associated with chronic inflammatory fibrosis of the retroperitoneum and the abdominal aorta. This article sheds light on the role of radiological imaging in retroperitoneal fibrosis, names various differential diagnoses and provides an overview of drug and surgical treatment options.

Methods A literature search for the keywords “retroperitoneal fibrosis” and “Ormond’s disease” was carried out in the PubMed database between January 1, 1995 and December 31, 2019 (n = 1806). Mainly original papers were selected, but also reviews, in English and German language, with a focus on publications in the last 10 years, without excluding older publications that the authors believe are relevant to the topic discussed in the review (n = 40).

Results and Conclusion Ormond’s disease is a rare but important differential diagnosis for nonspecific back and flank pain. Imaging diagnostics using CT or MRI show a retroperitoneal mass, which must be differentiated from lymphoma, sarcoma, multiple myeloma and Erdheim-Chester disease. Patients have an excellent prognosis under adequate therapy. FDG-PET/CT or FDG-PET/MRT should be considered as potential modalities, as hybrid imaging can evaluate both the morphological changes and the inflammation.

Key Points: 

Citation Format

Current approach to diagnosis and management of retroperitoneal fibrosis

Retroperitoneal fibrosis is characterized by fibrotic lesions around the abdominal aorta and common ileac artery causing ureteral obstruction. Secondary retroperitoneal fibrosis is associated with malignant disease, drugs, exposure to radiation and surgery. In contrast, the majority of retroperitoneal fibrosis is classified into idiopathic retroperitoneal fibrosis, for which immunological etiology has been suggested. Recently, idiopathic retroperitoneal fibrosis has been considered to be a spectrum of immunoglobulin G4-related disease, a systemic inflammatory disease, the concept of which has been developed during the past decade. In the management of retroperitoneal fibrosis, assessment of systemic lesions associated with immunoglobulin G4-related disease and the exclusion of secondary retroperitoneal fibrosis is mandatory. Histological examination of retroperitoneal lesions is desired for accurate diagnosis and management. Laparoscopic or open biopsy is often beneficial, although it is more invasive than needle biopsy. Treatment for idiopathic retroperitoneal fibrosis consists of meticulous glucocorticoid therapy based on that for immunoglobulin G4-related disease, which is expected to be highly effective. Ureteral obstruction is usually managed with conservative procedures, such as ureteral stenting or percutaneous nephrostomy. The goal of treatment for retroperitoneal fibrosis should be freedom from the stent/nephrostomy with withdrawal of the glucocorticoid in addition to salvage of renal function; however, conservative management does not always provide favorable outcomes. In contrast, aggressive surgical treatment, such as ureterolysis, can achieve the goal; however, the procedure is associated with high morbidity. Establishment of a consensus about treatment for idiopathic retroperitoneal fibrosis, including the optimal indications for the invasive surgical procedure and conservative management, is desired.

A case of retroperitoneal fibrosis secondary to chronic periaortitis

Retroperitoneal fibrosis is a rare inflammatory disorder causing increased fibrotic deposition in the retroperitoneum, often leading to ureteral obstruction. We present a case report of a 33-year-old male with 2-month history of back pain. Initial imaging showed thickening around the infrarenal aorta. Six months later the patient presented with renal failure; a CT abdomen revealed extensive soft tissue mass around the aorta resulting in ureteral obstruction. Histology results of biopsy of the soft tissue mass revealed retroperitoneal fibrosis. It is important for clinicians to treat periaortitis early as this can prevent progression to retroperitoneal fibrosis which can cause severe secondary complications such as renal failure from ureteral obstruction.

Retroperitoneal fibrosis in the era of immunoglobulin G4-related disease

Background

Retroperitoneal fibrosis (RPF) is a rare disease characterized by fibroinflammatory tissue in the periaortic or periiliac retroperitoneum, where it frequently encases ureters. There is emerging evidence that a subset of this disease is part of a spectrum of multisystemic autoimmune diseases collectively referred to as “immunoglobulin G4 (IgG4)-related disease”.

Methods

We retrospectively analyzed 27 idiopathic RPF patients and identified a subset as IgG4-related RPF, which we categorized according to recently published comprehensive diagnostic criteria. We compared clinical and laboratory characteristics and response to treatment between the two groups.

Results

Of 27 total patients, 16 (59.3%) were diagnosed as having IgG4-related RPF, and these were predominantly male. They were also significantly older and more likely to have other organ involvement, hydronephrosis, and postrenal acute kidney injury (AKI) compared to those with idiopathic RPF. However, there was no difference in response rate to systemic steroid treatment.

Conclusion

IgG4-related RPF accounts for a substantial portion of RPF cases previously identified as “idiopathic RPF” in Korea. Clinical and laboratory characteristics of IgG4-related RPF are similar to those of idiopathic RPF except for a striking male predominance, older age, and higher incidence of postrenal AKI in IgG4-related RPF. More comprehensive, prospective studies are needed to clearly distinguish IgG4-related RPF from idiopathic RPF based on clinical manifestation and to further assess treatment response and long-term prognosis.

The value of 18F-FDG PET/CT in the distinction between retroperitoneal fibrosis and its malignant mimics

OBJECTIVE

To discuss the utility of ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computerized tomography (PET/CT) in the diagnosis of idiopathic retroperitoneal fibrosis (iRPF).

METHODS

IRPF patients diagnosed between September 2011 and June 2016 were included. Retroperitoneal malignancy patients were included as control. The morphological features and FDG uptake of retroperitoneal lesions were measured along with lymph node (LN) mapping.

RESULTS

Seventy-one iRPF patients were included. Fifteen lymphoma patients and 6 retroperitoneal metastatic malignancy patients were included as control. Significant differences in morphological features were observed between iRPF and lymphoma but not retroperitoneal metastatic carcinoma. Compared with malignancy, iRPF displayed a lower frequency of high-FDG-uptake retroperitoneal lesions (P = 0.017) and a lower mean maximum standardized uptake value (SUV_max) (P < 0.001). LNs located at axillary, retroperitoneal, supraclavicular, inguinal or peritoneal sites were more frequently observed in retroperitoneal malignancy, therefore, were defined as specific LNs. The area under the curve (AUC) for SUV_max was 0.893 with a sensitivity of 85.7% and a specificity of 80.3%, when the cut-off value of the SUV_max was 6.23. The AUC for the logistic regression model combining the lesions above renal arteries, the SUV_max and the number of specific LNs was 0.987 with a sensitivity of 90.5% and a specificity of 98.6%. The risk stratification model analysis indicated that most of the retroperitoneal malignancy patients were at moderate or high level, while most of the iRPF patients were at low risk.

CONCLUSIONS

Retroperitoneal malignancy can mimic iRPF morphologically. ¹⁸F-FDG PET/CT can help to distinguish iRPF from retroperitoneal lymphoma and metastatic malignancy.

[18F]-Fluorodeoxyglucose Positron Emission Tomography in the Diagnosis, Treatment Stratification, and Monitoring of Patients with Retroperitoneal Fibrosis: A Prospective Clinical Study

BACKGROUND

The ability to distinguish malignant from benign retroperitoneal fibrosis (RPF) and to select patients who are likely to respond to steroid treatment using a noninvasive test would be a major step forward in the management of patients with RPF.

OBJECTIVE

To prospectively evaluate the potential of [18F]-fluorodeoxyglucose positron emission tomography (FDG-PET) to improve clinical decision-making and management of RPF.

DESIGN, SETTING, AND PARTICIPANTS

A total of 122 RPF patients were assessed and managed by a multidisciplinary RPF service between January 2012 and December 2015. Of these, 78 patients underwent 101 FDG-PET scans, as well as computed tomography and blood tests. Management was based on the findings from these investigations. Median follow-up was 16 mo.

RESULTS AND LIMITATIONS

Of the 24 patients with negative [18F]-FDG-PET, none (0%) had malignancy on biopsy (negative predictive value 100%). [18F]-FDG-PET identified malignancy in 4/4 patients (100%) before biopsy. All four patients had highly avid PET (maximum standardised uptake value ≥4) with atypical avidity distribution. [18F]-FDG-PET revealed avidity in 19/38 patients (50%) with normal inflammatory markers and no avidity in 10/63 patients (16%) with raised marker levels. Patients with highly avid PET were significantly more likely to respond to steroids compared to those with low avidity (9/11 [82%] vs 3/24 [12%]; p<0.01) or negative PET (9/11 [82%] vs 0/14 [0%]; p<0.01). Limitations include the small number of patients and the predominance of tertiary referrals, which may represent patients with particularly problematic RPF.

CONCLUSIONS

This study has established a promising role for [18F]-FDG-PET in optimising and individualising the treatment of RPF.

PATIENT SUMMARY

This study shows that [18F]-fluorodeoxyglucose positron emission tomography scans could reduce the need for biopsy in patients with retroperitoneal fibrosis (RPF). This technique can distinguish cancer from noncancerous RPF, and may be better than blood tests in assessing and monitoring RPF. It also appears to predict a patient's response to steroids, which should allow more individualised treatment.

Ultrasonography for Preoperative Diagnosis of Retroperitoneal Fibrosis

This study aimed to assess the application of ultrasonography for preoperative diagnosis of retroperitoneal fibrosis (RPF). A total of 51 patients with clinically suspected RPF underwent transabdominal ultrasonography and ultrasound-guided histopathologic biopsy (tAU-UGHB). Retroperitoneal fibrosis was diagnosed in 35 patients; of these, 31 cases (88.6%) received a diagnosis using tAU-UGHB. The ultrasonographic images mainly showed solid, irregular isoechoic masses, which were present behind the retroperitoneum and surrounded the abdominal aorta, inferior vena cava, and ureters and had clear borders with the encapsulated structures. Compared with other retroperitoneal lesions, RPF lesions were mainly located below the initial level of the renal artery, and their internal flow signals were not rich (P < 0.05). Retroperitoneal fibrosis had characteristic ultrasonographic features, and color Doppler ultrasound-guided biopsy could be positioned accurately, safely, and efficiently; therefore, tAU-UGHB can be used as an effective modality for preoperative diagnosis of RPF.

Idiopathic retroperitoneal fibrosis and its overlap with IgG4-related disease

Retroperitoneal fibrosis (RPF) is a rare disease characterised by fibrous tissue proliferation in the retroperitoneum, with encasement of the ureters and large vessels of the abdomen as the most destructive of potentially severe complications. It can either be idiopathic, or secondary to infections, malignancies, or the use of certain drugs. The idiopathic form accounts for approximately 75% of the cases, and is usually responsive to immunosuppressive therapy. In recent years, the emergence of a new clinical entity, IgG4-related disease (IgG4-RD), shed light on many fibro-inflammatory disorders once thought to be separate clinical entities, although frequently associated in the so-called multifocal fibrosclerosis. Among these, together with sclerosing pancreatitis and cholangitis, pseudotumour of the orbit, idiopathic mediastinal fibrosis and other conditions, is idiopathic retroperitoneal fibrosis (IRF). Both IRF and IgG4-RD can be associated with a wide variety of disorders, usually governed by immune-mediated (and particularly auto-immune) mechanisms. In our review, we discuss the clinical and therapeutic challenges IRF presents to the internist, as well as the meaning of its recent inclusion in the IgG4-RD spectrum from a clinical practice standpoint.

Retroperitoneal fibrosis - the state-of-the-art

Retroperitoneal fibrosis (RPF) is a rare disease, hallmarked by inflammation and deposition of fibrous tissue around the abdominal aorta. This process may spread contiguously and involve adjacent structures, leading to many complications, among which the most frequent and most severe is ureteral obstruction. The condition usually has idiopathic origin (idiopathic retroperitoneal fibrosis – IRF), but can also develop secondarily to a number of factors. The etiology of the disease remains unclear. Current research suggests that about half of the cases of IRF may be a symptom of a recently discovered, clinically heterogeneous immunoglobulin G4-related disease (IgG4-RD). Corticosteroids are the first-line treatment for IRF, but effective attempts to use immunosuppressants are also made. This paper presents the current state of knowledge on the etiopathogenesis, clinical presentation, diagnosis and therapeutic possibilities in different forms of RPF. Based on the latest research, an analysis of the relationship between IRF and IgG4-RD was performed.

Retroperitoneal fibrosis: retrospective descriptive study on clinical features and management

INTRODUCTION

Retroperitoneal fibrosis (RPF) is a rare condition characterized by the presence of inflammatory and fibrous retroperitoneal tissue that often encases the ureters or abdominal organs. This study describes the clinical characteristics, diagnostic methods, and treatments and their effects on renal function.

METHODS

We conducted a retrospective analysis of patients diagnosed with RPF at Maisonneuve-Rosemont Hospital.

RESULTS

We identified 17 patients with RPF between 1998 and 2013. Eight patients were females (47%), and the mean age was 62±18 years. Eleven patients were idiopathic. Back pain was the most common symptom. All diagnoses were made based on the finding of a retroperitoneal mass on the computed tomography scan. Three patients had histological diagnosis of RPF and seven patients had unspecific changes on their biopsy. Twelve patients needed double-J stents, three patients had a temporary percutaneous nephrostomy, two patients had to have a nephrectomy for refractory ureteral obstruction, and one patient required hemodialysis. Ten patients with idiopathic RPF received medical treatment. In the treated group, only two patients had complete remission of the disease and five patients had improvement of their lesions. There were no deteriorations and only one relapse. Seven patients did not receive any treatment; two of them achieved complete remission, one of them deteriorated, and two of them had no changes.

CONCLUSION

Most of our cases of RPF were idiopathic. Almost all treated patients received prednisone and seemed to respond, at least partially. There was a lot of heterogeneity in patient management, which makes it difficult to compare treatment effects. However, treated patients seemed to have more favorable outcomes than those who were not.

Diagnosis and follow-up of idiopathic retroperitoneal fibrosis: role of (18)F-FDG-PET/CT and biochemical parameters in patients with renal involvement

Idiopathic retroperitoneal fibrosis (IRF) is a rare disease characterized by fibro-inflammatory reaction surrounding ureters and other inner organs with possible secondary renal involvement. Symptoms are aspecific and recurrent phases of activity are generally associated with elevation of inflammatory indices. 18F-FDG-PET is nowadays an important tool for the detection of this disease, allowing differentiation between metabolically active tissue and fibrotic one. The purpose of this study was to investigate the role of 18F-FDG-PET in the management of IRF and to evaluate possible correlations between biochemical parameters and PET/CT findings of disease activity. We enrolled seven consecutive patients with IRF (in five histology proved the disease) observed from 2003 to 2012 (5 M:2 F, mean age 53.8 years, range 44-86 years). All patients presented with fever as first symptom; two had obstructive renal failure requiring hemodialysis; one underwent monolateral nephrectomy for parenchyma infiltration; six presented ureteral involvement; three underwent ureteral stent placement. For each patient, during a mean total follow-up of 26.5 months we evaluated serum creatinine, BUN, Hb, RBCs, WBCs, PLT, CRP, ESR. Periodic 18F-FDG-PET/CT scans (every 5.9 months-mean) were performed in all patients. Statistical evaluation was performed using "stepwise regression" analysis. Steroids and immunosuppressive agents induced a progressive normalization of PET/CT scans in all patients at the end of follow-up. Stepwise regression analysis showed that BUN, serum creatinine and CRP only if considered together, significantly correlated with SUV max (p value = 0.000003057). 18F-FDG-PET is a useful tool for clinical decision making in patient with IRF, allowing to evaluate the efficacy of the pharmacological treatment and to detect early recurrences, to modify the therapeutic approach. Acute phase reactants are not reliable alone for the management and the follow-up as they are often not concordant with metabolic assessment of the disease. In patients with ureteral involvement, CRP together with BUN and serum creatinine has a significant correlation with PET/CT results, and can help physicians in therapeutic approach, better than a single parameter.

Drug-induced retroperitoneal fibrosis: short aetiopathogenetic note, from the past times of ergot-derivatives large use to currently applied bio-pharmacology

Among the secondary forms of retroperitoneal fibrosis (RPF), that drug-induced shows very intriguing aspects given both the broad range of involved pharmaceuticals and the considerable interest arisen from the related pathogenetic mechanisms. The particular incidence, in the last four decades past century, of the RPF due to long-term use of ergot alkaloid derivatives (ergotamine, methysergide, pergolide, bromocriptine, cabergoline) and specific L-dopa derived agents, such as methyldopa, as well as to different analgesics, came progressively down given that their long-term use for either the prevention of migraine attacks or the therapy of chronic pathologies (Parkinson's disease, prolactinoma, pain management, etc) has been, year after year, supplanted or even made unavailable in many countries. More recently, instead, the occurrence of the RPF has been sometimes identified with the use of antitumoral chemotherapeutics, such as carboplatin and methotrexate, and, just lately, as an unusual side-effect of certain biological agents, about which it is timely to go into specific pathogenetic problems in more depth.