Unenhanced helical CT in the investigation of acute flank pain

Can obstructive urolithiasis be safely excluded on contrast CT? A retrospective analysis of contrast-enhanced and noncontrast CT

PURPOSE

The aim of this study was to determine if contrast-enhanced CT can safely exclude obstructive urolithiasis in patients with flank plain. We performed a retrospective cohort analysis to compare the negative predictive values of contrast-enhanced and non-contrast CTs for the detection of obstructing urolithiasis.

METHODS

Through report analysis, we identified all non-contrast and contrast-enhanced CT examinations of the abdomen and pelvis performed on adult patients in the emergency department at a single, multi-site academic medical institution in 2017 with an indication of flank pain. The prevalence of obstructive urolithiasis in each group was calculated. We subsequently analyzed 200 consecutive studies from each of these groups (reported negative for obstructive urolithiasis) for negative predictive value calculation. Follow up abdominal imaging within 7 days from original presentation was used as a reference standard for analysis.

RESULTS

In the noncontrast group, 1 study out of 200 was false negative (negative predictive value = 99.5%). In the contrast-enhanced group, there were no false negatives (negative predictive value = 100%). The prevalence of obstructive urolithiasis was 44.0% (351/797) in the noncontrast group and 18.7% (86/459) in the contrast-enhanced group.

CONCLUSION

Our results suggest that contrast-enhanced CT can safely exclude obstructing ureteral calculi in the setting of acute flank pain. This finding is of clinical relevance given the inherent benefit of IV contrast in diagnosing abdominopelvic pathology.

The Accuracy and Prognostic Value of Point-of-care Ultrasound for Nephrolithiasis in the Emergency Department: A Systematic Review and Meta-analysis

INTRODUCTION

Point-of-care ultrasound (POCUS) has been suggested as an initial investigation in the management of renal colic. Our objectives were: 1) to determine the accuracy of POCUS for the diagnosis of nephrolithiasis and 2) to assess its prognostic value in the management of renal colic.

METHODS

The review protocol was registered to the PROSPERO database (CRD42016035331). An electronic database search of MEDLINE, Embase, and PubMed was conducted utilizing subject headings, keywords, and synonyms that address our research question. Bibliographies of included studies and narrative reviews were manually examined. Studies of adult emergency department patients with renal colic symptoms were included. Any degree of hydronephrosis was considered a positive POCUS finding. Accepted criterion standards were computed tomography evidence of renal stone or hydronephrosis, direct stone visualization, or surgical findings. Screening of abstracts, quality assessment with the QUADAS-2 instrument, and data extraction were performed by two reviewers, with discrepancies resolved by consensus with a third reviewer. Test performance was assessed by pooled sensitivity and specificity, calculated likelihood ratios, and a summary receiver operator curve (SROC). The secondary objective of prognostic value was reported as a narrative summary.

RESULTS

The electronic search yielded 627 unique titles. After relevance screening, 26 papers underwent full-text review, and nine articles met all inclusion criteria. Of these, five high-quality studies (N = 1,773) were included in the meta-analysis for diagnostic accuracy and the remaining yielded data on prognostic value. The pooled results for sensitivity and specificity were 70.2% (95% confidence interval [CI] = 67.1%-73.2%) and 75.4% (95% CI = 72.5%-78.2%), respectively. The calculated positive and negative likelihood ratios were 2.85 and 0.39. The SROC generated did not show evidence of a threshold effect. Two of the studies in the meta-analysis found that the finding of moderate or greater hydronephrosis yielded a specificity of 94.4% (95% CI = 92.7%-95.8%). Four studies examining prognostic value noted a higher likelihood of a large stone when positive POCUS findings were present. The largest randomized trial showed lower cumulative radiation exposure and no increase in adverse events in those who received POCUS investigation as the initial renal colic investigation.

CONCLUSION

Point-of-care ultrasound has modest diagnostic accuracy for diagnosing nephrolithiasis. The finding of moderate or severe hydronephrosis is highly specific for the presence of any stone, and the presence of any hydronephrosis is suggestive of a larger (>5 mm) stone in those presenting with renal colic.

Urolithiasis in the emergency department

Urolithiasis commonly presents to the emergency department with acute, severe, unilateral flank pain. Patients with a suspected first-time stone or atypical presentation should be evaluated with a noncontrast computed tomography scan to confirm the diagnosis and rule out alternative diagnoses. Narcotics remain the mainstay of pain management but in select patients, nonsteroidal anti-inflammatories alone or in combination with narcotics provide safe and effective analgesia in the emergency department. Whereas most kidney stones can be managed with pain control and expectant management, obstructing kidney stones with a suspected proximal urinary tract infection are urological emergencies requiring emergent decompression, antibiotics, and resuscitation.

Urinary tract stones

Urinary tract stone disease is one of the most common urologic conditions in the US, with a lifetime prevalence of about 13% for men and 7% for women. In this article we review the management of urinary tract stones and discuss when to seek urologic consultation. We cover epidemiologic data, stone types, presenting symptoms, imaging, metabolic evaluation and risk factors, and medical management strategies. We also discuss the indications for surgical intervention and the common operative procedures currently available.

Renal medullary carcinoma: unsuspected diagnosis at stone protocol CT

Renal medullary carcinoma (RMC) is an aggressive neoplasm occurring almost exclusively in adolescents and young adults with sickle cell (SC) hemoglobinopathies, usually sickle cell trait (SCT) or hemoglobin SC disease. The most common presentations are hematuria and flank or abdominal pain. It is a highly malignant tumor, and responses to chemotherapy are rare and transient resulting in a dismal prognosis. A high level of suspicion is necessary when evaluating at risk patients presenting with hematuria or flank pain, as currently it appears that only early diagnosis could potentially alter the outcome of this disease. We report a case of RMC in a young male patient with SCT, who presented to the emergency department with low back pain and microscopic hematuria, clinically mimicking acute obstructing urolithiasis. Our case emphasizes the need to consider alternate diagnoses when evaluating computed tomography scans for acute flank pain.

Definição do nível da junção ureterovesical pela tomografia computadorizada

OBJETIVO: Definir o nível da implantação ureteral na bexiga através da tomografia computadorizada. MATERIAIS E MÉTODOS: Através de tomografia computadorizada da pelve com contraste endovenoso de 46 pacientes (31 homens e 15 mulheres) com idade entre 18 e 45 anos, com pelo menos um dos ureteres contrastado pelo contraste excretado, medimos as distâncias do meato ureteral até o teto acetabular e a borda superior da sínfise púbica, além do volume da bexiga. Utilizamos o teste t de Student para avaliar se houve diferenças estatísticas entre grupos. RESULTADOS: O nível da implantação ureteral na bexiga foi, em média, 10,6 ± 8,1 mm abaixo do teto acetabular e, em média, 29,7 ± 9,5 mm acima da borda superior da sínfise púbica. Nos pacientes com volume de repleção vesical menor que 200 ml e maior ou igual a 200 ml os níveis da implantação ureteral na bexiga foram, em média, 11,6 ± 7,3 mm e 10,2 ± 8,4 mm abaixo do teto acetabular (p = 0,61) e, em média, 28,3 ± 7,3 mm e 30,3 ± 10,2 mm acima da borda superior da sínfise púbica (p = 0,52), respectivamente, e nos pacientes do sexo masculino e feminino foram, em média, 11,8 ± 8,0 mm e 8,3 ± 8,0 mm abaixo do teto acetabular (p = 0,17) e, em média, 27,7 ± 9,2 mm e 33,9 ± 8,8 mm acima da borda superior da sínfise púbica (p = 0,34), respectivamente. CONCLUSÃO: Calcificações localizadas abaixo de 3 cm do teto acetabular e abaixo de 1,5 cm acima da borda superior da sínfise púbica provavelmente não representam cálculos ureterais. O grau de repleção vesical e o sexo não interferem significativamente na posição do meato ureteral.

Imaging features of crystal-induced arthropathy

Crystal-induced arthropathies constitute a spectrum of inflammatory arthritides that is induced by cellular reaction to crystal deposition in and around joints. A variety of microcrystals may be deposited and can induce an inflammatory response. The three most common types of crystal-induced arthropathy are gout, calcium pyrophosphate dihydrate deposition disease, and calcium hydroxyapatite deposition disease. Each has a characteristic clinical presentation, crystal type that may be aspirated from affected tissues, and radiographic appearance. Each of these entities may occur as a primary abnormality or secondary to an underlying disorder. Sometimes these diseases may coexist in the same joint or individual. Imaging frequently plays a crucial role in the diagnosis of crystal-induced arthropathies and may help to monitor disease progression and treatment response.

Tomografia computadorizada sem contraste intravenoso no abdome agudo: quando e por que usar

A tomografia computadorizada sem contraste intravenoso tem sido freqüentemente proposta na avaliação inicial de pacientes com suspeita de abdome agudo, ocupando o espaço de outros métodos diagnósticos. Os autores apresentam uma revisão bibliográfica dos principais aspectos e eficácia da tomografia computadorizada sem contraste intravenoso no diagnóstico de apendicite aguda, cólica nefrética, diverticulite, pancreatite aguda, apendicite epiplóica, pneumoperitônio e obstrução intestinal. Discutem quais as vantagens e limitações desta técnica de exame, bem como seus aspectos práticos.

[Imaging techniques and their impact in treatment management of patients with acute flank pain]

The purpose of this overview is to provide a general summary of the imaging techniques applied at the Vienna Hospital for the investigation of acute flank pain and the diagnosis of stone disease and the evaluation of their efficacy and impact on therapy management. The number of publications on the issue of "intravenous urography (IVU) vs computed tomography (CT)" is abundant; in recent years, advocates of CT make up the majority. In the Department of Urology at the Vienna Hospital, conventional techniques such as ultrasound and IVU besides UHCT still play an important role. This overview presents the advantages and disadvantages of the various imaging techniques for diagnosis of stone disease and evaluates their significance regarding therapy management of patients with acute flank pain.

Investigation of acute flank pain: how do practices of U.K.and Irish urologists compare with those of transatlantic and continental European colleagues?

BACKGROUND AND PURPOSE

Noncontrast-enhanced spiral CT (NESCT) is more accurate and reliable than intravenous urography (IVU) in diagnosing the cause of acute flank pain. This study aimed to determine the impact of current literature on the choice of imaging modality used to investigate acute flank pain within the UK and the Republic of Ireland.

MATERIALS AND METHODS

A questionnaire regarding the preferred investigation for acute flank pain was sent to all consultant urologists registered as British Association of Urological Surgeons members.

RESULTS

Of the 548 consultants from 210 institutions surveyed, 293 (54%) from 171 (81.4%) institutions returned their questionnaires. Intravenous urography is used in the majority of institutions (146; 85.4%) for investigating acute flank pain. Only 18 (10.5%) use NESCT, while 4.1% use ultrasonography. Among those using IVU as the investigation of choice, the main reason given was limited CT services (82.4%). Others included familiarity with IVU features (51.2%), limited availability of radiologists for out-of-hours reporting of CT (26%), more rapid procedure (20.8%), lower cost (20%), and lower radiation exposure (19.6%). Only 52.4% of consultants using IVU would prefer NESCT if both were equally available.

CONCLUSIONS

Urography remains the commonest modality for the investigation of acute flank pain in the UK and Ireland primarily because of limited CT services and greater familiarity with the images. Given the opportunity, only half of consultant urologists would select NESCT in preference to IVU, suggesting that improving the availability of CT services alone may not lead to practice paralleling that of our transatlantic and continental European colleagues.

Mimics of Renal Colic: Alternative Diagnoses at Unenhanced Helical CT

During the past decade, unenhanced computed tomography (CT) has become the standard of reference in the detection of urinary calculi owing to its high sensitivity (>95%) and specificity (>98%) in this setting. Numerous diseases may manifest as acute flank pain and mimic urolithiasis. Up to one-third of unenhanced CT examinations performed because of flank pain may reveal unsuspected findings unrelated to stone disease, many of which can help explain the patient's condition. Alternative diagnoses are most commonly related to gynecologic conditions (especially adnexal masses) and nonstone genitourinary disease (eg, pyelonephritis, renal neoplasm), closely followed by gastrointestinal disease (especially appendicitis and diverticulitis). Hepatobiliary, vascular, and musculoskeletal conditions may also be encountered. Vascular causes of acute flank pain must always be considered, since these constitute life-threatening emergencies that may require the intravenous administration of contrast material for diagnosis. Radiologists must be familiar with the typical findings of urinary stone disease at unenhanced CT, as well as the spectrum of alternative diagnoses that may be detected with this modality, to accurately diagnose the source of flank pain.

Renal ultrasound

Renal US is one of several imaging modalities available to the EP in the evaluation of patients with acute urologic disorders. It offers excellent anatomic detail without exposure to radiation or contrast agents but is limited in its assessment of renal function. It is an important alternative to helical CT scanning for evaluating renal colic, especially in children and pregnant women. It has an important role in excluding bilateral renal obstruction as the cause of acute renal failure. It is likely that Doppler renal US also will take on a prominent role in the evaluation of renal vascular disorders. It already has become the standard of care in the management of renal transplant patients. Bedside emergency renal US performed and interpreted by EPs with limited training and experience is increasing in use and gaining acceptance. At present, the primary role of renal US is to identify hydronephrosis in patients with renal colic or acute renal failure but, in the future, its role likely will expand as technology advances and its use increases. In many patients, bedside renal US may obviate the need for further diagnostic workup and speed the diagnosis and treatment of an emergency patient.

Alternative diagnoses to stone disease on unenhanced CT to investigate acute flank pain

Acute flank pain is a common problem in emergency medicine. The most frequent cause is urolithiasis, but many other entities can cause the same clinical presentation. In many institutions unenhanced computed tomography (CT) of the abdomen is used in this setting. One of the major advantages of unenhanced CT is its ability to detect other pathologies causing flank pain. In this pictorial review, we present the CT findings of pathologies other than stone disease in patients with acute flank pain.

Distinguishing stent from stone: use of bone windows

OBJECTIVES

To present a simple method to assist in distinguishing stents or nephrostomy tubes from urinary tract stones. Non-contrast computed tomography (CT) is now routinely used for the diagnosis and follow-up of urinary tract stones. When stents or nephrostomy tubes are in place, it may be difficult to differentiate the stent from the stone.

METHODS

Three representative patients with ureteral stents or nephrostomy drainage catheters (stents/tubes) who were suspected of having residual urinary tract stones were studied by visualizing the suspicious density on CT. Abdominal windows were used for initial viewing, then bone windows were used, and the two techniques were compared. The Hounsfield units (HU) of the various stents/tubes were measured in vitro to establish reference points. The pixel densities of stones have a known range and, in our experience, may be as high as 1600 HU.

RESULTS

Using the abdominal window, no difference was observed in the radiographic appearance of the stents/tubes compared with urinary calculi. However, when viewed in the bone window, the stone appeared less dense than the stent/tube. The in vitro pixel densities of the stents/tubes measured 1600 to 2600 HU compared with the calculi, which do not exceed 1600 HU.

CONCLUSIONS

Using the abdominal window, stents and stones may have the same CT appearance. However, the bone window allows a visual distinction between a stent/tube and a stone. This distinction is accounted for by differences in pixel density. This observation allows one to distinguish a stent/tube from a stone on CT in patients in whom a nephrostomy tube or ureteral stent is present.

Multidetector CT urography: techniques, clinical applications, and pitfalls

For two decades, computed tomography (CT) has challenged intravenous urography (IVU) in the evaluation of urinary tract abnormalities. Compared with IVU, CT is more sensitive and specific in the detection and characterization of a variety of urinary tract disorders, including renal masses and urolithiasis. The last purported advantage of IVU has been its ability to depict subtle and mucosal abnormalities of the urothelium. Now, using multidetector CT (MDCT), this challenge has been overcome. In this article, we review the current role of MDCT urography in the evaluation of the urinary tract.

Online radiology appropriateness survey: results and conclusions from an academic internal medicine residency

RATIONALE AND OBJECTIVES

This study was performed to evaluate the ability of medical trainees to choose appropriate diagnostic imaging studies for patients with various clinical indications.

MATERIALS AND METHODS

Twelve clinical scenarios were excerpted from the 2000 edition of the American College of Radiology appropriateness criteria and arranged in multiple-choice question format. Summary answers based on the criteria were written. The questionnaire and answer key were placed online and linked; the answer key was viewable only after all 12 answers were submitted by the trainee. An invitation to participate in the online survey was forwarded to medical house staff.

RESULTS

Sixty-five (43.3%) of 150 potential respondents completed the survey. The results were tabulated for all respondents and separately for each postgraduate-year class. Fewer than 50% of the respondents correctly answered more than half of the 12 questions. The average number of questions answered correctly by 1st-year residents was 7.02; by 2nd-year residents, 7.5; and by 3rd-year residents, 7.9.

CONCLUSION

Medical house staff are not adequately prepared to choose appropriate imaging examinations for specific indications. Improvements in education could prevent inappropriate use of radiology resources. Imaging centers might want to consider developing online catalogs to assist clinicians in choosing appropriate imaging tests.